I dynoed my bolt on 8.1/Ally today

Haulin' 8.1 · February 4, 2007

Well not much hoopla, just giving an account of what I've put on and it's benefit. Some searching here and on PerformanceTrucks.net indicates that a stock 8.1/Ally will put down 240 RWHP. Horsepower Engineering here in Houston was doing a dyno day special so I paid $10 for two pulls. Both runs were in 4th gear, tow/haul on to lock the converter, and from 3700 RPM through 5250 (Chuck didn't know any better and it hit a rev limiter lol) The 2nd pull was better as Chuck improved the technique a little after the first.

Peak #'s were 274 RWHP @ 4075 and 355 RWTQ @ 4075 on a Dynojet, 62*F, 30.2 in-Hg, 20% Humidity. SAE 0.95

That would indicate a 34 HP increase with my mods. Volant with ram-air tube in bumper, Ganetelli old school MAF, BBK 80mm TB w/port matched intake manifold, Champion 8.1 spec. copper plugs one heat range colder than stock, Delphi Marine 8.1 injectors at 39 PSI (flow is 10% richer than what the PCM expects), Hypertech programmer on 89 octane tune, and a Magnaflow x path muffler. I ran 93 octane Chevron during the test and engine and trans were at full operating temp 195 & 180.

HP stayed above 250 throughout the entire run and #'s actually started climbing steeply at 4800 where the Ally shifts but then fall just as fast as the fuel injection puts on the brakes by 5250.

TQ dropped below 300 at about 4650.

I was kinda bummed because I expected more based on how the truck performs but it's all torque so it's making good power just at a low engine speed. But at least I know it's up like I felt over stock. The best part of the experience was watching one of the techs setting up the runs open the hood. He didn't know anyone was watching and he still did one of those wide eyed WTH? stares at the big engine for a few seconds before it registered what he was looking at. They had never seen a 8.1/Ally truck there before.

Vernon

billcar9999 · February 4, 2007

I know you can get more with a better tune. I've been playing with HP Tuners and the results have been great. I get better mileage and much better performance now.

Haulin' 8.1 · February 4, 2007

I plan on getting a full tune when I go all out this summer. I still need the cam and headers then I'll do it all at once, gears, heads, and blower included. The Hypertech is just keeping my speedo honest and allowing me to do 100+ MPH for now.

Vernon

Cheekster96 · February 4, 2007

Howdy.

I would have thought that the big block would have put out higher torque numbers. I guess the Ally robs alot of that power and torque.

Was curious what the big block does on the dyno.

Cool numbers, thanks.

Lee

DiegoYJ · February 4, 2007

Interesting. It's nice to finally get some first person info.

I am curious to know which mods add the most ponies and which ones don't help much. It would be nice to have the use of a dyno for a day or two to experiment with which combos work the best and what kind of real world numbers most popular bolt-ons create as opposed to the manufacturers claims and net hype.

Haulin' 8.1 · February 4, 2007

Howdy.

I would have thought that the big block would have put out higher torque numbers. I guess the Ally robs alot of that power and torque.

Was curious what the big block does on the dyno.

Cool numbers, thanks.

Lee

Lee, TieRod said the same thing on performancetrucks.net. It made me think since he would be the one to know. So I looked at the dyno print out again and this is what I think happened. Since the shop owner was inexperienced with the 8.1/Ally combo he didn't start the pull until about 4000-4100 and tried to rev it way high. The peak numbers I got were actually right where he started the pull. I have a feeling if the pull had been started lower in the power band my numbers would have actually been higher, especially the torque. I think he started past the torque peak. TieRod says in his experience it should have been about 10HP and 30 Lbs.Ft. higher, which is probably what it would have done around 3500.

So if you guys ever get yours on a dyno and the guy asks if there's anything special about driving it on the dyno here's two things to remember.

1. Tow/Haul enguaged to lock the convertor.

2. Start the pull as low as possible to avoid a downshift into 3rd. Say 3,000 or so.

Vernon

Haulin' 8.1 · February 4, 2007

Interesting. It's nice to finally get some first person info.

I am curious to know which mods add the most ponies and which ones don't help much. It would be nice to have the use of a dyno for a day or two to experiment with which combos work the best and what kind of real world numbers most popular bolt-ons create as opposed to the manufacturers claims and net hype.

The mods I've think made the most impact was the Ram Air Volant, the hypertech after the cold plugs, and the larger injectors with the maf. I don't like cold thermostats due to increased engine wear but the colder plugs do the same thing for the tuner but better. With the crap alcohol gas now the factory tune is lean, and throw on a MAF and it gets leaner, plus the tuner and you're so lean knock rules. So the oversized injectors at the right pressure, stock is 60ish, flow enough to bring it back to knock resistant slightly rich.

Stuff works but you have to make it work.

Vernon

dewfpo · February 5, 2007

Thanks for the data Haulin' 8.1.

DEWFPO

Steel Chicken · February 5, 2007

Thanks for the info.

I'm not planning on doing any mods to mine (the GTO gets all mod money!!!), but im pretty good with HPTuners and im going to do some baseline pulls and then tune the hell out of it.

couple of things to keep in mind...you mention a few things (I did x mod which will make it lean) and (I did y mod to make it rich)...

the PCM will always gravitate to what its tuned to be...so even if you do some mods to rich or lean it out, after time, the trims will gravitate towards whatever the PCM is programmed to do.

The trick is to make mods that improve airflow, and let then tune the PCM towards a more aggressive tune (not so rich like factory stock, add some timing, reduce TM, etc).

Im just starting to learn about these trucks, and ive heard that their torque management is one of the biggest power killers. I even remember someone saying something about power enrichment totally turned off! As a consequence there should be alot of gain just with a good tune.

1st step, I need to go get a baseline...