Took my car for a couple of runs on a chassis dyno yesterday and got some disappointing results. The peak horse power is not what I expected, but the torque curve and peak was the severe let down.

Motor specs:

• 512 low deck stroker
• 10.5:1 compression
• OOTB Eddie 84cc heads
• Comp XR280 roller cam - .541/.537 lift - 230/236 duration @ 0.050
• Holley Sniper EFI

Gary at Jake's suspects the torque converter for the lack of a broad flat torque curve. It's a Turbo Action 17809ST tight converter. I reused it from the build before swapping to the big block stroker.

You guys got any ideas? The results are with the exhaust dumps open on the car flowing though 1 7/8" primary mid length headers.

Thanks.

Heck, not a big block guy, but before drivetrain loss that looks like about 500 horsepower with stock eddies and a tiny camshaft on pump gas.
Sheesh, not so terrible..... lol

Not a big fan of chassis dynos or any for that matter other than for getting a fuel and timing map cos I put down 458+ tq and hp and go mid 9's at 3000+ lbs.........

Out of the box Edelbrock heads aren’t the best head to go with on a Stroker engine

Any AFR readings to go with the runs?
What was the timing and its advance curve set at?

I'm no expert at this, but I would willing to guess the Sniper EFI hasn't 'learned' enough yet, or the ignition curve is way too slow.

Take it to the track, see what it runs. That's the number that doesn't lie and can't be fudged by the operator.

I know I'm leaving power on the table with them, but their flow rate at my max cam lift should be capable of supporting more than 500HP. Besides, the peek number could just be a tuning issue. I wasn't happy about not producing more than 1 HP per cubic inch, but not having that broad torque curve is really what bums me out and what I'm trying to answer.

Timing was 24 degrees initial with 34 total. I forget what the curve is set at. I'll go back over my notes and come back.

AFR during the pull was 12.5 as reported by the Holley ECU.

I've got the data logs off of the sniper for that dyno run if anyone wants more specifics.

Post up what your air fuel ration looked like, what was your target set at?

Sorry, just edited my previous post to include it. Target and actual were 12.5 during the pull.

I only used a chassis dyno once and it was a 4-speed car. I've seen weird data from chassis dyno tests of auto-trans cars w/ any significant stall speed and don't put much faith in those tests as a result.

that's 500+ hp & torque at the crankshaft. with everything hooked up (mufflers, alternator, water pump, etc) and in the chassis I don't think that's terrible. go back and look at fuel delivery, mufflers, etc. that's not much cam for 500+cuin.

On a Dyno Jet, they read on the high side,about 10% less than crank,, 400 hp / .90 = 444 net hp @ crank, most all other Chassis dyno read about 17 % less than crank HP.

Chassis dyno numbers can be really weird with an automatic. I don't think I'd worry about it just yet. How does it drive? How is the Sniper working so far? Are you controlling the timing with the Sniper?

Did you record data logs for each dyno pull? If so you can open up the config file on your computer and then play back the data log. That will allow you watch what all of the sensors are saying during the dyno pull. I'd pay attention to the AFR and MAP to see what they say. Do you have fuel pressure hooked up to the Sniper so you can data log it too?

I think you'll have a great combo once you get it all dialed in. If you want to make more power down the road you can get the heads ported and go up one size on the cam and you'll be around 600 hp at the flywheel.

That’s a really small cam in a 505.

I would be looking at 600ft/lbs and somewhere around 500-525hp on the engine dyno.

My guess is you’re just driving through the converter, giving you that low tq reading at the wheels.

It would be interesting to see what it would ET at a drag strip.
I've never raced a dyno.

Hi Andy, it drives great. Plugs are burning good, throttle response crisp. I don't do many full throttle blasts on the street though. Timing is still controlled by the distributor.

I've got data logs for the last two runs. Second before last was through the mufflers and only netted 370 peak horse power. The car has 2.5" exhaust and I kind of knew it would be a restriction. The last run is the sheet I attached to the first post in this thread - it was with the exhaust dumps opened up.

AFR during the pull was 12.5 and the MAP was 95 kPa. Fuel flow stays within a few lbs of 294 lb/hr.

My Dad had his car run on the same dyno last year. It's a 408 roller with similar cam specs. His peak numbers were less than mine, but it made gobs of torque through the range - noticeably higher than mine. This is really what I'm trying to figure out. I can attach the data log if it helps.

I really appreciate you guys helping me out with this.

-Mark

This is what the shop owner theorized. It is a tight converter.

I get what you guys are saying about getting it to the track. I got a friend who is going to bum me a set of Mickey ET Street tires for a trip to Ubly sometime in August.

You have way too small cam......for sure !

I would have gone in the 255* at .050 area minimum....75 lbs of tq lost there.....JMO...

Dan

Go to the track and have some FUN with it.

I helped a guy with a 505 build last fall.
Not a great overall combo, but some of it was a situation of reusing parts on hand.

Rpm’s with a bowl blend and valve job, original Torker, 850vs carb, 1-7/8” headers, .480 hyd cam.
I told him 600tq/500hp.

Made like 615/510.

You’ve got a better cam, his had better heads.

I’m sure with a more substantial cam and an rpm intake the one here would have been at least 50-75hp better.

As mentioned, chassis dynos and automatics can produce strange results, especially with a loose converter.

Looks to me like your converter slipped to around 5300 RPM, where both curves hook, and your TQ and HP were already falling off. I think its very unlikely that engine peaks torque at 5300 RPM.

What exactly is the converter? According to TA that converter is for a late model Hemi or Magnum setup... if this is the correct converter its going to stall way higher than it is designed to stall behind a 318-360 cubic inch engine.

Tq and hp are always exactly the same, and cross paths at 5252rpm.

I think you have a great combo for the street. Get out there and enjoy it this summer and then decide if you really want to change it. A bigger cam will make more peak power but you might lose some low end torque. Drive it for a while to see what you think before you make up your mind. You might just like the smooth idle and bottom end grunt that you get with a smaller cam.

with this combo I would be cautious about over gearing and too loose of a converter. on an engine dyno this engine may show close to 550hp. i'd try to sneak up on the total timing some; maybe try 36-37 degrees. you can get 2 1/2" mufflers that will flow better than some 3". I wouldn't get lost in the peak horsepower/rpm thing. whatever gains you might be making above 5200rpm may be ate up driving the trans/axle. chassis dyno thing is a different world than the more common engine dyno numbers. in my opinion, chassis dyno is real world and engine dyno can be more pie in the sky.

Why is everybody afraid to try and put some timing in it? Is it an internet myth or something?

I've tested BB ignition timing many at the track and on multiple race gas and pump gas engines on a engine dyno, all of the ones I tested like between 34 and 36 BTDC total timing for the best ET, MPH and HP and torque on the dyno.
This is with the TDC verified to make sure zero on the timing tab and balancer where accurate, I have found many engines that they where off also
I raced a 1963 415 HP Max Wedge car in NHRA stock for many years, a friend and fellow SS racer had a 1963 Savoy 415 M.W. he raced in Super Stock and swore his motor liked 42 degrees total timing I learned later he didn't build his motors and it had a late model timing cover with a early dampener, which ends up indicating 10 degree more timing than actual
IHTHs

Here’s that one from last fall, with a 2” super sucker on it:

Pulling up his runs out and doing the conversion to mph and looking at comparing to rpm and doing the math this thing is just blowing threw converter. looking at the graft you can see it is trying to couple up then it finally does when it starts running out of power.

Does the dyno have the ability to plot drum RPM vs. engine RPM? That would probably show what is going on.

Andy that's basically what we did and came up with the results. I didn't know how to do that so when my dyno operator came in and he did it and showed me.

So just to take a guess, at 3000 engine rpm the drum is barely moving. Since the drum is barely moving the recorded HP is low, but really the engine is making a bunch of power. It is just the that engine power is being absorbed by the torque converter (turned to heat in the tranny fluid) rather than turning the drum.

If that is what is going on then he needs a much tighter converter. Maybe a stock Hemi converter or something even stouter like a truck converter. With 500 inches and a small cam there is going to be a lot of torque on hand right off idle.

I don't think that that converter was designed for that much torque and it would not couple up. I would think that it just needs a converter more designed for that application and not one that was met for a small block. he probably could still get by with something that would be in the 3200-3800 rpm.

AFAIK, the dynojet doesn’t have any load cell to “take a reading” and measure torque.
It uses a formula to calculate the speed differential over time, and calculates how much power it takes to accelerate the drum(which has a known mass) that amount, in that amount of time(not a good description I know).
Basically, the rate of acceleration is what’s used to calculate the power.
It’s an inertia dyno.

If you run two cars with noticeably different power levels, say 100hp and 800hp, through the same rpm range(like 2500-6500), you’d notice the lower power car took much longer to get from 2500-6500.
The only thing controlling the “rate” is the weight of the drums and the output of the motor.
More power accelerates the drum faster.

I’m not sure all dyno jets operate this way, but the one my friends have does.

Edit: I did a little search and it appears Dynojet does offer some of their dynos with eddy current loading, along with the inertia loading.
With eddy current loading, it would be capable of taking an actual torque reading.

Something is wrong.
Not only are the numbers disappointing, the torque curve should NEVER have a big spike like that.

You are correct. they do have a load cell option but I have never seen one, every one I have used & seen was just the drum.

I know of a few cars that got run over at my friends shop where the numbers just didn’t make sense(weren’t right).

One that comes to mind was a 69 charger with a 446. Rpm heads, 509 cam, headers, 850 demon carb, 3.91’s, 10” converter.
It was something silly like 285hp.
The car actually ran pretty good on the street. This was an all steel, full interior street car.
Had to weigh at least 3800 with driver.

Went high 11’s at the track.

That’s not 285rwhp doing that.

FWIW...my cuda made 636 hp and 555 ft lbs of torque on the local Dynojet.
Ran 9.54 at 140.4 mph at 3800 lbs in that configuration.

Outran a bunch of supposed 800+ hp at the wheels cars too.

866Fwhp

60 Foot E.T. : 1.33
1/8 Mile E.T. : 6.02
1/8 Mile Trap Speed : 112.96
1/4 Mile E.T. : 9.54
1/4 Mile Trap Speed : 140

It actually went 1.320 to the 60' and 6.05 at 112.9 to the 1/8. Your calculations look good to me, lol. Always figured it was in the 850 hp range.

Wallace calc, but only 1 of them, been using it for years, has been pretty accurate for my old cars and others....Moroso chart differs, less hp etc.

http://www.wallaceracing.com/accel-calc.php

Input weight and then adjust hp no.

This thread has taken a bit of a detour....... but.....

572 I built, 918 on the engine dyno, 778 on the dynojet.

8.33@165, @2700lbs

Shows 930 on the moroso chart

yep slight detour, thats interesting, more hp than the engine dyno, normally reverse of that, but thats the BIG mph, light car doing that I presume, 165 would normally be 8 teens.....I made it 988.

That looks strange to me too. I would think smoking the tires on the dyno? Were you running street tires or race tires?

I was posting my results just to say not to get discouraged w/ low numbers from a chassis dyno. Always felt like my car ran a lot better than the chassis dyno numbers would suggest...considering the crap you see blasted all over the internet and magazines.

When it comes to racing and car stories I always try to remember the old adage about believe nothing you hear and only half of what you see

Here's an ancient sheet of mine from Jake's for comparison.

It would do me some good to head back there.

I don't really dig the spike in the curve from the original post, I have no idea what is going on with that but maybe someone does. If that was mine, that would be the first thing I'd point at and ask questions about.

That 5th Avenue big block sounds cool as heck, I'd really like to check that out sometime.

zippy, what converter is in your car?

It's a tighter than normal turbo action "J", 9". Originally it was custom built for a much more radical combination. Around 4400-4600 in this car, feels surprisingly tight on the street and can be easily driven normally without alot of slippage at light throttle, etc.

I know the dyno sheet can be configured differently than what the OP has shown.

I’d like to see a graph where the x axis is speed(mph), and another where it’s time(seconds).

Those should give a much better illustration of how the converter is behaving.

When the converter is pretty loose, and you’re using time or speed as the x axis....... the torque line will just go pretty much straight up at the hit of the throttle.....then kind of flat line until the driveshaft speed more or less catches up with the motor.

Thats interesting, that shows about 16% drop from moroso slide to wheel. & about 15% from dyno to wheel, all very close. very cool

Another thing to keep in mind when looking at chassis dyno results, from an inertia dyno, especially when a fairly high stall converter is used...... the data on the sheet starts when the button is pushed, which is often prior the gas pedal hitting the floor.
In that scenario, the numbers on the sheet below stall speed are at less that wot.

This is how you can end up with these oddly shaped graphs.

It’s not the same type of test as if there were a load cell and the throttle could be opened, the load stabilized against the brake, then released....... so that all data on the “run” would be at wot....... and the bottom of the run would start at stall speed(which could easily be at a higher rpm than where the motor makes peak tq).

Absolutely, send me a PM. I'd be game for hanging out sometime.

So the most likely culprit is the converter then. I'm open to opinions on what to run. It's a bit weird since I have a lock-up 46RH transmission in the car. Current gear is 4.10, but I wouldn't mind going back down to a 3.23 providing I can get that torque curve where it should be.

I'm looking at a track day next month also. I'll have time slips before I spend anymore money on parts.

Thanks guys.

See if Jake can email you another sheet or two where the x axis’ are speed and time.

Do you know if the button to start recording was pushed before or after getting to wot?

My “opinion” on it is...... if the motor were tested on an engine dyno, the numbers......as well as the shape of the curve....... would look very similar to the sheet I posted.

A drum-RPM vs Engine-RPM comparison could show if there's any transmission or tire slip on the dyno.

In what gear was the run made?
Haven't seen it mentioned but I presume it's not a manual valve transmission, so maybe the throttle linkage is/was adjusted back a little too much to prevent a downshift during the run?

low gears and loose converters can give lower than expected numbers.

This is a pretty good read:

https://www.google.com/amp/s/www.hotrod.com/articles/hrdp-0405-chassis-dyno-guide/amp/

I've had my Dart on a hub-mounted Eddy-dyno about 3 sessions already.
It at least takes out the possible tire-slip (not that the engine in the car would be able to spin the wheels on a regular dyno that is...).

The HP and torque cross at 5,252 - always, they're supposed to (if using std. notation).
What reason is there for violent peak torque at the same place: 5,252?
None I ever heard of - tht's very close to the point of maximum VE.
With that small a cam, torque should be nearly flat from 3,500 up (not 200 @ 3,500) and fade slowly after 5,000 (the curves after 5,252 look possible if disappointing).
I don't know what a bad (mechanically failing) converter will do, but I never heard of a converter that sucked up 50% of the power @ 3,500 RPM (200 vs. 400).

If you look at the runs zippy posted, the curve starts down under 3000rpm, and shows about 200ft/lbs.
Obviously that part of the recorded data is not taken at wot....... since the car has a 4600 converter.

Any data under the stall speed is not an accurate picture of the power at wot....... since you can’t be at wot and under the stall speed at the same time.

A quote from the article in the link:

Okay...... after sleeping on it, I think I can better explain how you can have an inertia chassis dyno sheet where the power curve is not at all representative of what the engines power curve would look like, including have a big spike much farther up than where the engine tq peak is.
This is basically all pertaining to running a high stall converter on an inertia dyno.
One of problems is how the graph is displayed.
Without any time element to the graph, it doesn’t paint an accurate picture of how the run progresses from start to finish.

First we have to understand that the torque converter is the coupler that connects the engine to the load....... and that the stall speed determines at what point(rpm) full load will be applied.

Secondly, on an inertia dyno, the power is determined by the rate of acceleration of the drum.
Nothing is “measuring” the power output.
Accelerate the drum at a higher rate, power displayed goes up.

If you did a test with these parameters, you would get a dyno sheet that showed very low engine output at the lower rpms of the graph(and have no bearing on what the engine power would be at those points).

Assume the engine in the car has already been on an engine dyno and makes peak tq between 3000-3200 rpm(not that this matters, I’m just using it as an example to point out that even with a peak tq of a known lower rpm point, a loose converter will show peaks at a higher point than where they actually happen).
The car it’s installed in has a converter with an actual flash stall speed of 5000rpm.
The test will be conducted from 1200-5500 rpm.
The car will be in high gear, throttle held steady at 1200, drum speed stabilized, you push the button to start recording just before you push the throttle down....... the motor accelerates to 5500rpm, you push the stop button.
The data recorded will be from 1200-5500rpm.
On the tq/rpm graph, the point where the full load is applied to the motor(5000rpm) will be most of the way to the right side of the graph.
And there will be a big spike in output right at about that point....... because that’s where the converter started to couple, and the big change in acceleration to the drums occurred.

You could pick points along the graph at the lower rpms where the numbers were much much lower.
That’s because with the converter slipping so much, there isn’t much change in acceleration rate at the drum. The converter is still flashing up to stall speed and is not very effectively coupling the motor to the load.
The graph would have a lazy slope from 1200 to the point near where the converters stall speed is........then as you approach the stall speed, converter couples, drum rate surges, and you get a spike on the graph nowhere near where the engines actual tq peak is(in this example).

Here’s why this is not an accurate picture of how the run really happened, and why looking at a graph of the run with a time element attached helps tell the story.
When the start button got pushed and the throttle went to the floor, the motor immediately went right to the 5000rpm stall speed.
If the motors tune was sharp, that would happen in less than one second(1200-5000)....... yet it takes up 3/4 of the space on the tq/rpm graph.
If you plotted rpm on the y axis and time on the x axis, the line would go almost straight up from 1200-5000(and would all happen way at the left side of the graph), then at whatever rate the power being produced from 5000-5500 could accelerate the drums.
If the motor was making pretty good power, this whole run from start to finish would be maybe 2-2.5seconds...... because the load would have only been applied from 5000-5500rpm.

It’s not a long steady pull like the tq/rpm graph depicts, and the numbers below stall speed aren’t representative of engine output whatsoever.

The OP’s motor should have an engine output torque curve similar to the one I posted the sheet for.
That one had peak tq at 4000 rpm. At 5000 it’s already down 93ft/lbs from peak.
If you chassis dynoed that motor in a car with a 5000 stall speed converter, that’s where the highest torque will be displayed, since the torque curve is already well past peak, and that’s the lowest rpm where full load can be applied.

The other thing the rpm/time graph does is give you a nice picture of what the flash stall is.

What I’d like to know from the OP is, what’s the flash stall speed of his converter.
If you haven’t tested it yet, try this......
Disconnect the kick down linkage, put the car in drive...... let it up shift into 3rd...... hold the throttle at about 12-1500rpm and let the speed stabilize...... then floor it, and observe how high the tach needle “flashes” to.
For all practical purposes, that’s your flash stall speed....... i.e. the lowest rpm that full power can be applied to the wheels.

Alright, I think I'm following here. The torque converter isn't coupling until well past the torque peak of my motor, and when it finally does at 5200 RPM is the reason we see the spike.

This is the same converter I was using behind the old small block. It wasn't advertised as stalling that high, but the additional torque of the new motor pushed it that high?

So this is exactly what Gary meant when he said it was driving through the converter?

I can call Jake's on Monday and see if I can get those graphs.

Some additional information: tires are 285 Nitto NT555, kick-down cable was disconnected from the throttle body, overdrive was turned off and the pulls were made in third gear.

On an engine dyno, the throttle goes to wide open and the motor is allowed to stabilize against the load before the “pull” is started.
Most pulls are done from low to high rpm.
As long as the pull starts at an rpm lower than where the motor makes peak torque, you’ll get a good picture of the shape of the power curve, and where the peak occurs.

With a chassis dyno that has these same capabilities........being able to hold the load against the absorber to get things stabilized....... then starting the pull from that point....... the beginning of the pull would always be whatever the converter stall speed was.
That would always be the lowest rpm where output was recorded(if the test was conducted in that manner).
So if you had a 5000 stall converter, there wouldn’t be any data below that point.

Again, if the engines peak tq was well below that rpm...... that would still be the point on the sheet where the highest tq was observed...... and would in no way reflect where or what the engines peak tq output really was.

That’s how it appears to me.
By the looks of the graph, I’d say it starts to couple effectively at about 5000, and at around 5200 or so when it’s more fully locked up, it’s well past peak tq and you’re well into the downhill side of the tq curve of the motor, which is why it’s dropping off quickly right after it shows the peak.
It’s not until the converter is basically locked up that the power curve will mimic the engine power curve........and in this case that seems to be happening well beyond the engines tq peak rpm.

You should do the flash stall test to see if it agrees with what appears to be happening on that sheet.
I can’t believe there is any way a converter that was “right” for a small block would be correct behind a lower/mid rpm high torque 511.

I’m not sure exactly what kind of driving experience you’re looking for, but the OD trans and 230@.050 cam, unported std port heads, dual plane manifold....... kinda looks like a 3000-ish flash stall combo to me.
Which would likely be a pretty tight(very tight?) 11” unit.

As an illustration of how tq affects stall speed, the 8” converter I ran behind my 340 and then the 383.
4800 behind the 340, 5400 behind the 383.

Depending on what your what your SB combo was, I can easily see where the 511 could be 200ft/lbs better, especially down near where the converter would have stalled behind the SB.
And a difference in tq like that will have a huge impact on how the converter behaves.

Frankly, I’d think it should be pretty high on the list of things that should be changed.

i was thinking the same thing when i asked zippy what stall converter he has, if you look at his graph, it's about 5000rpm where the curve starts to look like what you see from an engine dyno.

in my opinion, the 4.10 gears have just as negative effect as the converter. mushy converter plus low axle gears reduces the drum rpm and acceleration rate. I don't think that engine needs either of these two factors. a lot of cubes and small cam should be a torque monster. I have a simplistic philosophy about some of this; you can let the engine do the work or you can work the engine. I think in this case the lower gears and looser converter are working the engine instead of letting it work. this engine probably makes gobs of low and mid-range torque and probably could be tuned to work with a stock 11 3/4" converter. add a 3.23 or 3.55 gear and I bet results will be different.

Exactly.
If you notice, there is a little upturn in the curve right about where he says the stall speed is.
It isn’t necessarily that there is a spike in engine power output at that point, but rather a spike in the acceleration rate of the drum, because of the spike in converter efficiency.

It would be interesting to see a rpm/time graph of one of those runs.
If the button were pushed right before going to wot, that area from about 3200-4800 probably happens in less than one second.

Lew, I agree.
With a stock/tight 12” converter and 3.23’s behind the OP’s combo........ the curve wouldn’t look anything like what he posted.

I’d love to see a torque/hp vs time, and torque/hp vs speed graph of that same pull at the beginning of the thread.

I think the rpm vs time graph gives the best picture of how the converter behaves.

3.23 gear, 1900 rpm stall. Pull done in second gear.


Mustang, not DynoJet

Russ, what are the dips on the upward slope...... tire slip?

it's my understanding that mustang dyno's are a little stingy compared to dynojets.

when I went thru the chassis dyno thing some years back I was looking for information to try and figure out which direction to go in. good information costs money and time. treat the exercise as part of the learning curve and make the meaningful changes for best results.

I can't get away with using a factory big block converter - my 518 is a 23 spline lockup variety. If I attempt to go back to a factory converter for this trans it would be one that was built with small blocks in mind. Is this a problem?

Sounds like you need to talk to some converter shops.

I would say, telling them the motor should produce around 600ft/lbs at 3200-4000rpm is a pretty safe bet when discussing your combo and figuring out the converter requirements.
I’m guessing it will be one of those “as tight as we can make it” situations.

Yeah, you're right. I'm looking over what is available for 23 spline 727/518 at Turbo Action and there is only one in three different configuration: regular, medium and tight. I already have the tight one, so now I'm thinking there is something wrong with it.

I got a couple calls to make tomorrow. I'll get back to this thread with what I find.

How does it drive on the street? If it drives okay at part throttle that might be a clue. If it is so loose that it feels like you're driving a rubber band then that would be another clue.

I don’t know why you wouldn’t just go out and try the stall test.
It’s free, easy, only takes a few minutes, and would give you valuable info.........for having a phone conversation with a converter shop, or just for knowledge about the overall combo.

Not to mention, if the converter flashes way less than 5000, then that dyno sheet becomes even more puzzling.

Edit: I went to the TA site...... looks like their 518 converters are 10”.

I would expect a motor combo like yours to flash a tight TA 10” to around 4000-4200 doing the high gear test.

Sorry if I missed this in another post, but aren't the rollers on the dyno jets like 5000lbs? It might be a case of the converter being ok on the road but gets pushed through with the load of the dyno drums.

I had a compton converter 2800 lock up in my A518, I now have a 4000 lock up that was built for my combo,it works awesome, PATC brand. 512 lowdeck

That 2800 would probably work well for the OP.

If he was closer I would give it to him, it still worked great.

I believe it was from the way we throttled up. We stepped it up to get above 3500 before dropping the hammer because my full auto tranny would otherwise kick down to first.

they look like shift spikes to me,....?

Seriously? I would be more than willing to compensate you for your time and shipping.

Andy, the converter feels fine out on the street, but I never really take it to full throttle.

Why not?
how are you going to know what it does on the street at WOT so you can provide some feedback to the converter shop that your dealing with?

No-one picking up on the bold-text?

I say there's a great possibility the transmission was slipping also.

I thought it was well-known fact one never disconnects the Throttle Pressure linkage on a Mopar transmission, unless you have a modified valvebody.

Could be Lew. But that would make the pull in 3rd, plus one.

you may be right. no shift spikes.

I just pulled my dyno sheet out and there are only 2 shift spikes. I was guessing. I may try to post my sheet. the spikes are clear to me on my sheet.

hopefully this is clear. the humps are shift spikes.

The reason the kick down is disconnected is to allow the trans to shift into high at a low rpm and hopefully stay in high after going to wot.

Lew, what was the change from November 98 to May 99?

I had a suspect head gasket on the #1-#7 side and changed gaskets, one of my pocket port jobs (don't laugh) and a hugh's/engle 2330 cam (replaced the 272/.455 cam). think it picked up 38hp at the wheels. those numbers are spike readings and don't count. real horsepower was around 325-327. they couldn't get a tach reading so I had to do the math for rpm. things started to go flat around 4300rpm.

I know you want to prevent kickdown from happening at a dyno-run, but disconnecting the linkage totally is not the way to do that. You should just do some short tip-in testruns to re-set the linkage so it doesn't downshift.
I've had my car on the dyno and with just 2 or 3 dry-runs the downshifting was taken care off.

Lowering the transmission's oilpressure and make it unsusceptible to throttle changes, just when you're about to do the most straining test of all on the driveline (just when you need the most clamping force/oil pressure on the clutches) isn't the healthiest situation for the trans.

As far as the horsepower goes, I wouldn’t expect this combo to make much more than 400whp.
I agree with others. You need a much tighter converter.

The problem with trying to “ramp up” on a dynojet is, the bearings for the drum are extremely low resistance.
It takes much less energy to turn the drums at driving speeds than it does to push the car down the road at those same speeds.
So, if you gradually ramp up to wot, by the time your foot hits the floor the rollers might be going 50-60mph.
This loads the converter in a way the will provide lower numbers, because there is less speed differential between the engine and input shaft(less tq multiplication), as well as allowing the motor to be at an even higher rpm.
This is similar to trying to do the high gear stall test while going 50-60mph.
The observed flash stall speed will be higher and you’re not going to get an accurate picture of the true stall speed.

The only real “load” you get from a dynojet is when trying to change the speed of the drum.
You don’t get to ramp up to wot against a predetermined start rpm like you would on a dyno with a load cell.

With a high stall converter, the longer it takes and the higher the speed of the drum before you get to wot and pushing hard against the weight of the drums........ the smaller the window of usable data there will be on the sheet.

I think it would be somewhere in that range, but since the curve is already sloping downward slightly after the converter starts locking up, it would appear the peak is probably slightly below 5200rpm....... at the wheels.
On the chassis dyno there are a lot more variables that determine where it happens.
I would have expected 530-540hp..... maybe 550, from that combo(using the car headers) on the engine dyno here....... then it’s usually about a hundred less at the wheels for a typical street/strip car at that power level.
So, I would have thought 425-440rwhp....... which I could easily see happening with a tighter converter....... something that had the load coupled to the motor at wot several hundred rpm below the point of peak hp.

Of course........ that doesn’t mean it wouldn’t be quicker at the track the way it is now....... especially since to this point, we don’t know what the actual flash stall is.

If you poke around a while on the net you can find a lot of info......
I saw one thread where someone was testing a car with a lockable converter.
There was over 100ft/lbs observed difference between locked and unlocked in the lower rpms....... with locked being the higher numbers(displayed on a tq/rpm graph).

Have the dyno shop E-Mail you the data files.
Goto Dynojet and download the WinPep 7 Dyno Run Viewer software on your computer and you can display the run data in different forms.

http://www.dynojet.com/downloads/downloads.aspx?dc=Software/Firmware

When I ran on the chassis dyno, I was told to roll into the throttle, not stab it. I haven't had issues with spinning the tires on the dyno rollers with the Charger that has M/T Street ET tires, but my Truck with street tires (Cummins TD) would spin the tires on the rollers if I "stabbed" the throttle. This would looks alot like a really loose torque converter. That is why plotting power vs MPH may show how well the engine is coupled to the rollers might be converter or tire slippage, maybe even transmission clutch slippage if it is having issues?

That is very good to know, thanks! I called Jake's and left my email, so I should be getting the raw data files. Once I have those I'll post up the graphs: RPM vs time and drum speed vs time.

Tonight I'll see if I can get the car out on some quiet stretch of road and deduce what the converter is flashing to.

I also dumped the video from my phone of that last pull:



Should have posted this sooner, sorry.

It’s rolling along pretty good before it goes to wot....... which should make the converter look like it has more stall on the sheet than it would “on the starting line”.

Looks like it’s at full power/load for about 4 seconds.
I’ve watched several times now...... you can hear the rpm hover a bit after it gets up on the converter, then start to accelerate afterward.
That point right before you hear the pitch start to change......that should be where the spike on the sheet is.

On an engine dyno, a 3000-6000 pull at 300rpm/sec rate would be ten seconds.

The motor sounds pretty good.
As long as nothing seems “broken”, I’d def head to the track before I changed anything.

$25 entry fee at the track, and we could have saved all this typing....lol....and had fun.

Yeah, but then you don't get those cool dyno printouts to show everyone.

Everyone knows a fancy dyno sheet trumps an ET slip every time.

Where were you 100 posts ago. That seems like a lot of work going to a race track and actually racing your 🚘

Waiting for the sequel.... unexpected time slip results

Here is what a chassis dyno session looks like with a manual transmission. This is some cam testing I did a long time ago.

You can right click on the picture to open in a new screen and then if that isn't big enough to see just use control and + command to enlarge.

Thanks for that Andy.

I still haven't heard back from the dyno shop about getting the raw data files. I'm going to give them another call today after lunch.

As for the guys that keep beating the 'take it to the track' dead horse already, I get it! I acknowledged this pages ago and stated a track day is on the list. I'm not one of those dyno sheet snobs that measures their self worth against a fancy print out. I only wanted to know what could be possible causes for the lack of a broad torque curve that these motors are known for.

I wouldn't worry about it. It is summer time, enjoy the car. If you find something you want to change then put it on the list for winter time. If you make it to the track great, but if not who cares. I don't feel a need to take my car to the track.

Do your thing however you want and enjoy.

if you ever do head out to a track, post up ahead of time.
It's a good vehicle for a "what will it run?" thread.

Lapeer is looking really nice these days....

i went to the track first, had a lot of questions and went to the dyno second. the track info/dyno info plus a few other tid-bits answered my questions. I agree with andy and zippy; just enjoy it! questions will be answered in time.

I wouldn't worry about it, you're simply asking for some help and the graph was necessary to facilitate the discussion.

This is the first time I've ever posted a power graph on any forum, and have never made any dyno hp claims in any post on any of the stuff I've had on either an engine or chassis dynos. And like Lew, these pulls were after about 30 passes at the track, and the dyno session was for testing purposes, not bragging rights, so I know he's not talking about me.

I like having my cake and eating it too.

I want the big dyno number...... and the low time slip. 😎

I have to admit, there is a little satisfaction and fun in having the lowest hp dyno sheet, but holding the quickest and fasted et slip.........and that's with a heavier car to boot.

You do present a very good argument 🤓

And of course, that’s a way better scenario than having the big dyno sheet number........ and the slow time slip.

I think you done pretty damn good with a fat car, no gear, and stock exhaust!