Very nice! ^ That is more of what I was expecting to see, a curve rather than a plateau.

Yes actually my 2.5gallon cell was very low on that last test and fuel pressure dropped to 3 psi. I topped it up but will not be running it again until Friday when the customer comes by to witness and load it up. Good eye. I have the wideband results on that test at the shop but it may not line up to what the fuel turbines recorded. Thanks again for your assistance. J.Rob

Did you perform any mods to the intake or did you leave it as shown in this pic ?

I’m speaking about the area under the carbs.

A carbide burr and sanding roll never went near it. Just bolted a 1/2" spacer under each carb for clearance. I wasn't really after ultimate power with this--It's just a street car 1970 Challenger --I'd like to keep this customer around awhile longer. J.Rob

Did manage a video earlier today. 572 Hemi/Dyno

Nice work Jesse,

Big improvement in the right direction. The power curve looks almost identical to mine ; peak tq @ 4500 & peak hp @ 6000. I'm sure the customer will be very happy. Sounds nice on the dyno ! Will you be running it again on Friday (Dec 11) ?



Ron

Yes running it tomorrow, the one and only dyno session the customer has been to was when this engine ran so poorly. This is the example in the graph and that was after a full day of chasing problems and the tune--It started out much much worse. It was safe to say he was disappointed. Hoping to make a much better impression tomorrow. Take care, Ron, J.Rob

K

Not criticizing the manifold, just trying understand why a similar manifold on a motor I did last year was fat.

I keep leaning this thing out and it kept making more power but I ran out of runway and had to take the motor off the dyno.

My BSFC looks terrible to me. No runner bungs for EGT, just one in each collector.

Well we did notice the dual widebands were nearly identical bank to bank under all conditions BUT WOT. Under WOT the Driver's bank was a full point richer than the Passenger side. I think its just a quirk of the dual plane design and I too have run out of time to explore it further. We had to richen this up a little and it seemed to make a touch more power everywhere but mainly to keep it a little safer for the end user. My carb guy is great and set these 600's up ahead of time so secondary fuel adjustments were easy. J.Rob

Very nice! It should be a blast to drive.

Here are the last few pulls. Went from 32 to 30 degrees, went from short to long clusters, raised the oil pressure from 50’s to 80’s (same pull that I went from 32 to 30 - shame on me for two changes for same pull). Notice the BSFC - fat no? EGT ran from 790-992, highest it got was 1029.

Thread derailment!!

In reference to Transmans post about the carb tuning and bsfc.
It’s not a good idea........ since its not directly indicative of whether or not the carb is rich or lean.

Example....... imagine the motor on the dyno, steady state run at 5000rpm, making 500hp, using exactly 250lbs/hr.
So, the bsfc is .500.
Let’s say there is a wideband reading in the pipes and it’s showing 12.5:1.

Now............we attach a big hyd pump to the front of the crankshaft.
One that uses up 100hp@5000rpm.
So, with the pump attached to the front of the motor(eating up 100hp), the dyno only registers 400hp on the load cell.

The motor is still actually making 500hp, using the same amount of fuel and air it did before, and is still the same a/f ratio....... but since the dyno only registers the power as 400hp(because there is a 100hp parasitic draw on the front of the motor)the bsfc is now .625.
But...... the motor is not running any richer.

Bsfc is an efficiency reading...... the result of measured power vs fuel consumed.
Nowhere is the ratio of air to fuel referenced to arrive at a bsfc number.

Sure.......”generally” high bsfc numbers track with rich a/f ratios, but they don’t always.

I have tested a number of motors through the years that really didn’t like lean mixtures.
You’d richen them up....... a/f ratio reading would confirm....... motor would make a big move in inscreased power....... bsfc would go down.

What high bsfc numbers are really telling you is....... you’re not making good power for the amount of fuel you’re using.

Most of the stuff I test doesn’t make the best power when they’re getting into the danger zone for being lean.
That being said, I usually tune for best power, while making sure there is some safety margin built in by erring to the richer side.
And then the bsfc numbers just end up where ever they are.
If the motor makes pretty good use of the fuel those numbers will be decent........ and if it uses a lot of fuel but doesn’t make great power...... the numbers won’t look that good.

Thanks Dwayne, since it was my first dyno session in my life and I have looked at many here I had to ask the question.

As I stated earlier, it kept making more and more power as I leaned it out but ran out of time.
Back in the day we did all of this at the track, no one had dynos.

I always start fat worrying about the starving child/children then start leaning out.

Are there fuel flow and hp numbers to go along with those bsfc numbers?

And no a/f ratio measuring during that session?

By looking at how much higher the bsfc numbers are at the end of the pull, I’d say you were probably running the motor at a high enough to see the hp curve start heading down.
Even if the a/f fuel curve is pretty flat at the top end of the pull, if you’re running the motor high enough to see the HP start falling off...... the bsfc numbers will start to go up.
The rpm is going up, and as long as the valvetrain isn’t doing anything odd, the air flow should still be increasing with rpm.
More air flow pulls more fuel in with it.
So, you have air flow and fuel flow increasing..... at the same time the HP is decreasing........ and the result is the bsfc/bsac numbers are getting worse.
You’re using more air and less fuel...... and making less power with it.
Even if the a/f ratio was perfectly flat....... the bsfc/bsac numbers would still be going up.

|Whipped up some fuel lines for the customer so he doesn't have to run flexible braided stuff-he didn't want that. J.Rob

Those lines look awesome!

Yes, very nice

Thanks, they look better in the picture though. J.Rob

Forming lines like that is a "acquired" skill, not easy to be taught in a class room

Motor was making more HP but stopped the pull at 6500. It didn’t stop climbing from 4K to 6500. BSFC climbed slowly as well. Pulled the stick when it made 612 HP. I’ll send you some info by PM - don’t want to derail again.

Thanks Cab I think-lol.

Today was definately one for the Win column. Customer came in, I hit the button for the electric chokes, pumped the throttle twice and hit the switch. Engine fired and settled into a nice fast idle of about 1800 rpm. Let it run while I monitored dyno water , coolant and oil temps, jazzed the throttle twice and the idle came off the fast idle setting and proceeded to warm up at 1080-1100+rpm. Made a couple of short pulls from 3800-5000 to put some more temp in the oil and made a couple more from 3800-6000 without shutting it off. Best pull of the morning came in @ 734HP @ 6000rpm. We were all curious to see what would happen with the little air cleaners on because the first time around they were worth 40hp without them. It was a pretty nice outcome actually. Oh and as a bonus I think I sold his old crossram and carbs for him. J.Rob