Dyno results for 8.1L

gandolphxx · April 18, 2002

DYNO DAY in Houston - 330 RWHP [est. 450 Flywheel] - That was best in 2nd because of the d**n torque management and the speed limiter [ of all the ridiculous things]. They can't get RPM for torque because of my Nology wires - still trying to work around that. I am sure that there is more there once the limits are off - engine was only breathing hard before cut off.

BradyB - thanks for the benchmark - I didn't do mine before the SC - using yours. He is reporting 250 RWHP on a 345 HP engine, standard mods.

It is amazing that we have a 28% loss due to the monster tranny, but so be it - Corvettes run 18% [sigh].

I will repeat the process with speed limiter removed and post results shortly.

Any other 8.1L results - thoughts?

PS: Think it is time for the intercooler

Dihappy · April 18, 2002

DYNO DAY in Houston - 330 RWHP [est. 450 Flywheel] -

I will repeat the process with speed limiter removed and post results shortly.

Thats awesome Jack!

And a shame about the 28%

Hurry and remove that limiter

PS-Do you think upping the rev limiter will help any?

gandolphxx · April 18, 2002

Thanks Henry, I was pleased with the result given the TM limitations - I can't do much with the rev limits yet due to the Whipple programming - I am not convinced that I am hitting their presets yet - next step is the transmission and shift characteristics - that will be the test.

Now to figure out how to get the RPM

CMNTMXR81 · April 19, 2002

Awesome numbers! I take it you have the Whipple then?

If you think the 4L80E robs power, the Allison robs more power than many engines make period.

gandolphxx · April 19, 2002

Awesome numbers! I take it you have the Whipple then?

If you think the 4L80E robs power, the Allison robs more power than many engines make period.

Yes I have the Whipple, love it, and while the 4L85E [4L80E-HD] sucks power, I can imagine what the Allison does, but it sure can haul.

CMNTMXR81 · April 19, 2002

I bet you can lay a lot of tire down too!

I'm still on the fence as to whether I go into the motor or do a Whipple (with the intercooler of course).

gandolphxx · April 19, 2002

I bet you can lay a lot of tire down too!

I'm still on the fence as to whether I go into the motor or do a Whipple (with the intercooler of course).

Given the Allison's hunger, you would be best off with the intercooler - I am on the fence about it right now.

If you go into the motor, what would you do?

CMNTMXR81 · April 22, 2002

If I go into the motor, I'm not sure if I'm gonna punch it out any to say 540, or even more. It'd depend on how much room there is to bore it without running close to any waterjackets or oil galleries. One thing I will not sacrafice is durability. Whether I oversize or not, it'll be heads and cam at the least. Anything I do, it has to remain stone cold reliable which can be a challenge especially when upping the compression ratio and then tuning the PCM so as not to get any knock out of it especially under load (towing).

Going the Whipple and intercooler, I can leave the internals alone (therefore not worrying about reliability) and pretty much bolt on everything I need and the Whipple comes with it's pre-packaged tuning.

Either way, in the end, both will make roughly the same amount of power with a slight edge going to the Whipple (depending on how extravagant I go on the motor). I just mentally have a block against forced induction. I tend to be a "make all your power N/A" type which then swings my opinion back to heads and cam.

Decisions, decisions!!!

Kansas Kid · April 22, 2002

I got a couple questions/remarks about this thread. Do either of you guys know what the 8.1/auto usually lays down torque wise on the dyno? I could assume its around the same 28% loss through the drivetrain, which would put it at around 330 ft-lbs. But we all know what assuming does.

As for the auto transmissions, do either of you guys know specifically when they use the torque management. Like which gears, between shifts, etc. Does the Allison even use torque management with the 8.1? I don't keep up much on the gas side of these trucks, but I know about how the Allison acts with the Dmax. With the Dmax it uses the torque management in the first 2 forward gears, and it cuts power between shifts. The torque management is actually quite noticeable on the Dmax in first and second gear when compared to the 6-speed. Suprised the he!! out of me.

One last thing, and I am done. What does Whipple say the charger will increase Hp and torque by? Reason I am wondering is, the diesel guys have already found the limits of the Allison (didn't take long). The max limit before all #### breaks lose is 100Hp, so none of the boxes are pushing more then 80-90Hp. ATS already has the following stuff available for the Allison to handle upgraded power: triple disc lockup torque convertor ($1,370), electronic lockup controller ($275) and valve body ($630). Thats alot of money, for what these diesel guys consider a pretty modest gain in power. Not that 90Hp and 230ft-lbs is all that small, but the Dmax is just so easy to get power out of that being held back that early by the tranny is kind of disappointing.

btw, most Dmax/Allison trucks dyno 230Hp and 440ft-lbs. So maybe the Allison doesn't eat up any more power then the 4L85e does.... (thats still alot though)

gandolphxx · April 23, 2002

Sorry, I forgot to put up the "stock" numbers from another 2500 - 243hp and 352tq - again messed up by torque management. Whipple suggests a 40% improvement , my numbers close - will be better with speed limiter gone.

Hopefully I can get it dyno'd with the RPM to get torque, seems that the Nology wires are a challenge - trying to get workaround.

The torque management is in stages as I understand it:

1. PCM allows .6 sec for a .3 sec shift.

2. At WOT the PCM will get even more aggressive and feather cylinder firing. Takes a lot of practice to learn how to sneak up on it, but not trigger it.

The TM is so aggressive that it is not practical to dyno in 3rd - I have seen references to the increasing intrusion of the TM over the last three model years.

I am not familiar with the Allison, but suspect that the same conservative approach is taken by the engineers.

Actually the 8.1L is mated with a 4L80E-HD or 4L85E - beefed up the same as the 4L65E with the 6.0L.

Hope this answers most of the questions, if not fire away.

CMNTMXR81 · April 23, 2002

I'm kicking myself for not putting it on the dyno before I started doing stuff. Knowing the Allison robs more than the Hydramatic transmission, I think your 28% is a happy medium. I was gonna say more like 30%. Testing 28% on Gandolph's numbers, it's right on for the HP but his torque number is a bit higher.

The torque management only is affected in the 1st-2nd shift and the 2nd-3rd shift, albeit not as notciable. From there it shifts as normal. At least I can't feel any TM between 3rd and 4th. I personally feel it goes through 3rd, 4th, and 5th way to quick for me. But then I'm not used to a big block in a truck that's meant for hauling (therefore geared that way) and not speed.

Kansas Kid · April 24, 2002

I personally feel it goes through 3rd, 4th, and 5th way to quick for me. But then I'm not used to a big block in a truck that's meant for hauling (therefore geared that way) and not speed.

As in it doesn't hold the gear long enough, or it just accelerates so quickly that it goes through the gears quickly. I know alot of the guys with Dmax/Allison trucks I have talked to say that the transmissions shifts way to soon in the RPM band and could easily improve acceleration times by simply letting the motor wind out about 400-500rpm more in each gear. Of course getting into overdrive with 520ft-lbs of torque to push you isn't all that bad of a thing either...

CMNTMXR81 · April 25, 2002

I personally feel it goes through 3rd, 4th, and 5th way to quick for me. But then I'm not used to a big block in a truck that's meant for hauling (therefore geared that way) and not speed.

As in it doesn't hold the gear long enough, or it just accelerates so quickly that it goes through the gears quickly. I know alot of the guys with Dmax/Allison trucks I have talked to say that the transmissions shifts way to soon in the RPM band and could easily improve acceleration times by simply letting the motor wind out about 400-500rpm more in each gear. Of course getting into overdrive with 520ft-lbs of torque to push you isn't all that bad of a thing either...

You hit the nail right on the head. It seems to shift too soon (or at least sooner than I'd like). That extra 500 or so RPM would be nice.

I'm thinking some of this and the torque management may be controlled in signifigance by the "calculated load value" that the PCM monitors. When it reaches near 100% (which would be fairly easy with 455 and 520lbs of torque on it ) it goes to the next gear and in the process backs off timing between the shift.

Maybe I'll experiment with a log file on Autotap Sunday night if time permits.

gandolphxx · May 25, 2002

author=bradyb date=04/05/02 at 13:20
Okay guys my 8.1 is pulling 250 horses on the Dyno. I know that my drive line is built like a tank but 95 horses? That is a lot of drag. I guess it does take a good $5,000 to make your truck go fast. Don't get me wrong, I love my engine, it is so cool to go up a hill and not have the engine down shift, that 8.1 is a beast. Would it help if I disabled the torque management functions, any body done this? Would I destroy my transmission without torque management?

author=gandolphxx date=04/16/02 at 18:50

OK ... DYNO DAY in Houston - 330 RWHP 450 Flywheel - read it and weep! That was best in 2nd because of the damn torque management and the speed limiter [ of all the ridiculous things].

BradyB - thanks for the benchmark - I didn't do mine before the SC - using yours. It is amazing that we have a 28% loss due to the monster tranny, but so be it - Corvettes run 18% [sigh].

I will repeat the process with speed limiter removed and post results shortly. ;D

PS: Think it is time for the intercooler

UPDATE -Torque management ameliorated [gone], speed limiter gone, etc + Whipple intercooler.

RWHP 362 @4300 with 28% loss through drivetrain = 502 HP!

RWTQ 494 @3400

Making progress, sounded like a banshee @ 125++ or maybe a a bit higher.

SnakeEyeSS · May 25, 2002

sweeeeeet! Man, go burn some ford's! That's awesome, I bet that thing will tow a 12,000 pound anything without missing a beat. I'm guessing your gonna have some trouble keeping tires very long

Anyone know the drivetrain loss for 88-92 Silverado 350's with the 700-R4?