AZDoug

Numbers are RPM, w/ H pipe, w/o H pipe, at the rear wheels, through full exhaust, mufflers,and tail pipes, with 1.62" primary pipe Hedman headers

1500, 402, 225
1750, 400, 230
2000, 400, 300
2100, 405, 350
2250, 405, 340
2500, 405, 365,
2750, 405,380,
3000, 410, 400

3500 and up, they curves were pretty much parallel, peaking at 430 ft-lbs at 4300 RPM.

Doug

MikeM

I read that as someone has stuck a potato in one of your exhaust pipes and the "H" lets the exhaust by-pass to the other side.

Doug F.

...and the potato blew out at 3000+ RPM

62Jeff

I assume those are torque readings at each RPM range?

MikeM

Yeah, that's the way I see it. How 'bout giving us YOUR analysis of those figures?

MikeM

Yeah, that's the way I see it. Usually takes just about 3000 to do it. How 'bout giving us YOUR analysis of those figures rather than critique mine?

Dave64

Am I reading you right? The "H" pipe actually makes 177 hp more at 1500 rpm, or is the 225 actually pound feet of torque? If not, these numbers are absolutely phenomenal.

Dave

AZDoug

Those numbers are ft-lbs torque, with H paipe and w/o H pipe (old dyno run) not HP.

No potato in the pipe.

There was always a strange harmonic in the exhaust, even before the full exhuast was added past the mufflers and even with the old 327, it dropped in torque some and the A/F ratio went real lean at 2200 RPM, no matter how much fuel you pulsed in at that RPM range.

Having to lean out the part throttle fuel in that 2200 RPM range now with the H pipe, as it is too rich.

I can't explain it. Maybe get rid of the resonators (which were added after the EFI, but before the new motor), they helped with the 2200 RPM anomolie but didn't completely solve it. The resonators mellowed the sound quite a bit before the H pipe as installed, they are halfway between the collectors and the mufflers and are basically 8" long, 4" diamater wide spots in the pipes, but with sharp inlet and outlet inside the resonator.

Doug

Mark Lovejoy

I'm not sure of what engineering units are being used here.

But 400 ANYTHING at 1500 RPM is unbelieveable

AZDoug

I was driving down the street a few days ago at about 10 MPH and floored it.

I am not sure what exactly happened except I heard tires scream for half a second, the front of the car lifted quite high (I still have SSM lift bars on),a nd the shift light went on at 5600 RPM faster than I could react,a nd I finally found second gear about 6500 RPM and shut it down.

The Mickey Thompson SR 26X10 tires did not spin very long, they hooked up quite nicely. Never made it to 50 MPH so fast in my life

Doug

Kensmith

Those are nice numbers with the H pipe. Love the torque at low RPM. What are you running anyway? Hard to believe the H pipe would make that kind of low end difference.

KC John

Having been around engines most of my life, I'd have to say you either had a clogged muffler or resonator or a kink in one side of your exhaust system to make that kind of a difference.

It is fact that "X" pipes actually perform better as far as increasing HP and TQ. An "H" pipe has some benefit, but it usually can't be felt in the seat of your pants.

The numbers you posted looks like you put a blower on it. I'd be looking at something being clogged, or get your money back from the guy that did your dyno.

AZDoug

The straight thru Borla mufflers are not clogged, nor are the resonators, which are just empty pressure wave termination boxes, nor is there any kink or sharp bend in one side of the 2.5" exhaust.

The exhaust is all new within the past 2 years.

if there was a clog, we wouldn't have gotten identical 430 ft-lb torque numbers at 4300 RPM, with or without the H pipe, i don't think.

Same dyno, both runs, i was there for both.

Doug

AZDoug

427 SB. Very similar to lars new motor except wider bore, shorter stroke, and smaller headers, but EFI injected. Probably milder cam in mine.

The difference is there. Plug readings taken prior to H pipe install indicated both banks were equal (no restrictions of one bank over teh other.).

Doug

Doug F.

Mike: I think you are mis-interpreting my intention. I was agreeing with your analysis, and adding to it. My potato "blowing out" was to explain why the readings, with and without H-Pipe, were the same from 3500 RPM on up as AZDoug described. I am sorry for the confusion. Doug F.

MikeM

Oh! I guess I didn't think anyone else would see it like I did.

Stan's Customs

....and heavy on the unbelievable! Something isn't koshier here, seems to me. Are sure about the numbers on the first run Doug?

...don't suppose the dyno operator could be funnin' you could he?

...whatever is going on, if it will work on anything else ...your in line for some big bucks! I've never seen numbers change that drastically on anything....ever.... especially at what might as well be at an idle.

Stan

Doug F.

In all seriousness, somethings wrong. A crossover is worth maybe 25 ft lbs torque.

AZDoug

Numbers are right, here is a copy of the first Dyno run i posted last january.

Go back and re read my comments about the fuel pulse width and running too lean originally and couldn't get it rich enough in the ~2200 RPM range, and don't just focus on the raw numbers.

There is (was) some strange harmonic going on between the 1.62" headers and the Victor Jr intake in the low RPM ranges that the H pipe fixed. Same headers and same intake on both the 327 and the 427 and same weird ~2200 RPM problem, but the problem was worse on the larger motor.

Dyno from january 3, 2008:



Dyno from today:


Now look at the 327 Dynos, note the way high AF ratios, that were only brought into control by massive fuel added at ~2200 RPM, (and added fuel didn't help anything on teh 427 motor without teh H pipe).







Doug

AZDoug

In this case, it was worth 175 ft-lb, at least in low RPM ranges.

Mebbe y'all with a bunch of dog motor cars should consider an H pipe.

Mine was same diameter as the 2.5" exhausts, and located about 7" behind the collector flanges.

Doug