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Who has used a chassis dyno and did it help your tune?
#1440573
05/22/13 03:59 PM
05/22/13 03:59 PM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
OP
Taking time off to work on my car
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OP
Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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The local Import Tuner shop that did my Subaru WRX "makeover" last year has a chassis dyno. That got me wondering about whether it would be a benefit to strap The MoPig (once running, obviously) down on it to see how it performs, maybe get some baseline air-fuel curve #s, etc. Their shop foreman runs an Outlaw 10.5" Chebby, so it's not like they don't know what a carbureted American V8 is. Also, they seemed pretty interested in having my car on their chassis dyno after showing me videos of a 700+ RWHP modified supercharged Shelby 'stang on it. So, who here has used a chassis dyno and did it really help w/ getting your tune dialed in? Or should I save the $$$ for test & tune entry fees at the track and dial it in the old fashioned way? 
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Re: Who has used a chassis dyno and did it help your tune?
[Re: BradH]
#1440574
05/22/13 04:25 PM
05/22/13 04:25 PM
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Joined: Nov 2003
Posts: 1,969
Chandler, AZ
Duner
top fuel
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top fuel
Joined: Nov 2003
Posts: 1,969
Chandler, AZ
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Usually the track is too crowded to make enough passes to try different things to see what works best. So the dyno makes much more sense for tuning experimentation. You can see immediately what helps and what hurts without some of the inconsistencies that happen at the track if you are strictly comparing timeslips. The wideband and graphing capabilities on the dyno help a ton. The dyno has also helped me diagnose transmission problems correctly when I couldn't really pin down the problems at the track. Imagine what this felt like? hehehe  You will still need to play with things like launch rpm and tire pressures at the track - but at least you can already be done tweaking things on the engine.
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Re: Who has used a chassis dyno and did it help your tune?
[Re: BradH]
#1440576
05/22/13 04:30 PM
05/22/13 04:30 PM
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Joined: Jan 2003
Posts: 3,575
The Netherlands
BigBlockMopar
master
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master
Joined: Jan 2003
Posts: 3,575
The Netherlands
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This is not a dragracer, but just a dailydriver which I tuned for 1.5 year by ear, buttdyno, vacuum- and AFR-gauge. I went to the dyno just to get a baseline HP-number and to see what the low cr 318 still put out. At the location after the first run the shop-owner asked if I wanted to try something on the engine to see if there's more in it. I didn't bring anything useful but I decided to try some minute changes in timing and mixture adjustments. All the changes I did during the 5 consecutive runs made the engine put out less HP then the first run... Was nice to find out I have a well calibrated buttdyno...!  This reply is of not much use in a racecar but just felt like sharing anyway...   
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Re: Who has used a chassis dyno and did it help your tune?
[Re: BigBlockMopar]
#1440584
05/22/13 06:57 PM
05/22/13 06:57 PM
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Joined: Jul 2005
Posts: 1,301
Penna
70satelliteguy
pro stock
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pro stock
Joined: Jul 2005
Posts: 1,301
Penna
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"BigBlockMopar " Did the Dyno you used have a roof leak?  Mike
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Re: Who has used a chassis dyno and did it help your tune?
[Re: sixpackgut]
#1440586
05/23/13 12:35 AM
05/23/13 12:35 AM
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Joined: Jun 2007
Posts: 2,646
Plymouth Meeting, PA
bigtimeauto
Trophy Winner
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Trophy Winner
Joined: Jun 2007
Posts: 2,646
Plymouth Meeting, PA
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I chassis dyno lots of cars but you guys can keep your AF meters i pull plugs.
BB, TT5,Procharged 3300lb Street Car 4.79/154
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Re: Who has used a chassis dyno and did it help your tune?
[Re: sixpackgut]
#1440587
05/23/13 12:41 AM
05/23/13 12:41 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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I have been on a dyno twice... once was on Woodward ave. for a demo run for show and tell... my car got rained on sitting on my open trailer out there and it poured water in my dist... I didnt know this untill after I was up past 4000 rpm and it started breaking up... then I went on Jakes dyno a few weeks later just for kicks to see what it made 
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Re: Who has used a chassis dyno and did it help your tune?
[Re: sixpackgut]
#1440589
05/23/13 05:51 AM
05/23/13 05:51 AM
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Joined: Jan 2003
Posts: 32,394
Quicktree
I Win
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I Win
Joined: Jan 2003
Posts: 32,394
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Quote:
Quote:
i did, had the A/F perfect on the dyno. got to the track and it was almost a second slower. leaned it out and went back to where we were.
why would that be? were you tuning for most hp on the dyno or best A/F?
A/F with a new e-85 carb.not really concerned about hp. looking more for consistency
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Re: Who has used a chassis dyno and did it help your tune?
[Re: 70satelliteguy]
#1440590
05/23/13 06:13 AM
05/23/13 06:13 AM
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Joined: Jan 2003
Posts: 3,575
The Netherlands
BigBlockMopar
master
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master
Joined: Jan 2003
Posts: 3,575
The Netherlands
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Quote:
"BigBlockMopar "
Did the Dyno you used have a roof leak?
Mike
This was needed as extra cooling for the room to counter the heat from all that horsepower my little pony-Dart put out...
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Re: Who has used a chassis dyno and did it help your tune?
[Re: sshemi]
#1440592
05/25/13 08:11 AM
05/25/13 08:11 AM
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Joined: Aug 2004
Posts: 2,128
sweden
sshemi
top fuel
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top fuel
Joined: Aug 2004
Posts: 2,128
sweden
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Re: Who has used a chassis dyno and did it help your tune?
[Re: sshemi]
#1440593
05/25/13 09:04 AM
05/25/13 09:04 AM
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Joined: Feb 2010
Posts: 1,645
Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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Quote:
Sorry to highjack but while where on the subject.
I know of a chassie dyno pretty close to me and not very expensive but...
The guy have not lowered the rollers into the floor. So the car would be very tilted forward.
Would that effevt the carb in abad way???
I belive so cause the float levels would be very off.
What do you guys think???
Agree that tilted forward will effect the carb. A tilt back would at least be similar to the effects of acceleration. Floats are fairly centered and should not be too much effected but the fuel levels relative to the emulsion holes, etc will be - and this will effect the fuel curve. Likewise the fuel level above the front jets will be lower. Not ideal for a baseline.
To the OP: Useful - yes. Degree of usefull depends on planning the test sessions. It's usually a lot more $ than going to the track, but it lets you focus on tuning. So I think its a good start if you can afford it.
Bring jets, secondary springs if relevant, etcs. Inertia only dyno is really best for tuning WOT in 3rd or 4th gear. My preference now is to take a two runs and then disconnect the secondaries and jet in the primaries. Then add in the secondaries. Possibe detours include adjusting the timing and adjusting bleeds.
On the ride back home, be prepared for the possiblilty that the primary jets are too lean during steady highway cruising - the engine will surge as it comes off the transistion (somewhere around 3000 rpm). For this reason, I now tend to err on the side of rich when on the dyno.
In my experience, having the Innovate WBO2 will provide a quicker and more detailed response curve for AFR. Tailpipe sniffer is OK, but the bungs are nice for street and strip use. However it is almost a requirement to also have rpm recorded. With a typical dynojet WBO2, expand the vertical scale so AFR from 12:1 to 14:1 takes up at least half the screen. With AFR I'm looking for a flat stabile line and the AFR number is mostly a reference point to best overall torque and HP curves. As you can see in the above image, at least with dynojet - sometimes its easier to read using the MPH vs. HP. Ask for a copy of the files and software reader.
Here's an Innovate data overlay showing that the primaries providing a flat AFR curve but the secondary side is not.  Dynojet data shows the same thing. I'll try to attach.
Last edited by Mattax; 05/25/13 09:36 AM.
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Re: Who has used a chassis dyno and did it help your tune?
[Re: Mattax]
#1440594
05/26/13 12:41 AM
05/26/13 12:41 AM
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Joined: Mar 2009
Posts: 2,467
Sydney,Australia
tex013
top fuel
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top fuel
Joined: Mar 2009
Posts: 2,467
Sydney,Australia
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I use my engine shops chassis dyno often.
It is extremely useful for comparison use . I dont get goo wound up over actual rwhp shown . I look at afr to get in the ballpark . Comparison on changes , gain or loss .
Best use is repeatability right in front of you . You can do jetting and timing loops quickly and easier.
Tex
New best ET 10.259@129.65 .
New best MPH 130.32
Finally fitted a solid cam,
stepped it up a bit more
3690lbs through the mufflers
New World block 3780lbs 10.278@130.80 . Wowser 10.253@130.24 footbraking from 1500rpm
Power by Tex's Automotive
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Re: Who has used a chassis dyno and did it help your tune?
[Re: tex013]
#1440595
05/26/13 01:39 AM
05/26/13 01:39 AM
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Joined: May 2008
Posts: 5,399
Aurora, Colorado
451Mopar
master
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master
Joined: May 2008
Posts: 5,399
Aurora, Colorado
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Quote:
I use my engine shops chassis dyno often.
It is extremely useful for comparison use . I dont get goo wound up over actual rwhp shown . I look at afr to get in the ballpark . Comparison on changes , gain or loss .
Best use is repeatability right in front of you . You can do jetting and timing loops quickly and easier.
Tex
The drag strip is so packed anymore that you are lucky to get 3 or 4 runs in, and they are usually hours apart making it hard to see consistent back-to-back comparisons. On the chassis dyno, I can change jetting and timing several times in an hour, and at least have a known starting point on the tuning.
On the 500" stroked 400, i re-used the 950HP carb and jetted it richer for the larger engine just to be safe. Took the car to the chassis dyno, and ended up with about the same jetting the 451 was using. What the chassis dyno did not show was the carb wanted a bit more accelerator shot, so at the track, I changed the pump cam to the green one and it helped a slight stumble off the line.
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Re: Who has used a chassis dyno and did it help your tune?
[Re: BradH]
#1440596
05/26/13 03:34 AM
05/26/13 03:34 AM
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Joined: Jul 2005
Posts: 134
Flyover Country
340king
member
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member
Joined: Jul 2005
Posts: 134
Flyover Country
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I used a chassis dyno to well, tune the chassis on my circle track car. I really didn't even care about the engine output, as long as it wasn't rods! The usefulness of the tool is only limited by your preparation and ambition while on the dyno. I spent about a full day on the dyno sorting out different chassis changes. I filmed them for the purpose of reviewing the chassis response to the changes. There is a lot to learn or that can be learned. Good luck if you go. http://www.youtube.com/watch?v=_fn4_XhsTls
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Re: Who has used a chassis dyno and did it help your tune?
[Re: sshemi]
#1440598
05/26/13 03:11 PM
05/26/13 03:11 PM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
OP
Taking time off to work on my car
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OP
Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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Quote:
If i go i will try to find the best power with timing and to get a flat a/f curve.
Then change jets at the track for most mph.
Same here, along w/ possibly swapping carbs to see what differences result.
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