poorhousenext

Looking for thoughts on this. If chassis dyno used is spot on then max HP is within 25% drivtrain lost of GM's engine Dyno peak HP. 360 HP Vs 480 HP.

TQ on the other hand is 30% off peak engine dyno TQ. 329 TQ Vs 470.

What puzzles me is peak HP on GM's dyno sheet is at 5800 RPM. Peak HP on my sheet has moved out to 6506 RPM. I would have thought that peak HP like Peak TQ would still occur at same RPM as shown on Engine Dyno Sheet based on cam's design. Like everyone, I would have loved to see higher numbers. What I see is AFR is rich on low end, may be due to gear run was done in and/or exhaust. Any thoughts?





Transmission is TCI 6X and rear gearing is 3.55. Run was done in 4th gear (3.55 X 1.18 = 4.19 drive ratio. Since car will trap in 4th gear in 1/4 mile, 4th may have been the better gear to tune in anyway) rather than 1:1 5th gear and converter was not locked. TQ converter is a Circle D dual clutch billet aluminum stalled in 2500 - 2800 range. If your wondering why such a low stall RPM, it's due to the 6X close ratio gearing which provides great RPM retention between shifts compared to 4l65 & 4L80 transmission gearing. Also because car will be autocrossed, not just straight lined raced.

TCI 6X (4L80E based)
2.93
2.23 -- 76.10% (high) RPM Retention -- 23.90% RPM DROP
1.57 -- 70.40% (high) RPM Retention -- 29.60% RPM DROP
1.18 -- 75.16% (high) RPM Retention -- 24.84% RPM DROP
1.00 -- 84.745% (high) RPM Retention -- 15.255% RPM DROP
0.75 -- 75.00% (high) RPM Retention -- 25.00% RPM DROP

4l65/70
3.06
1.62 -- 52.94% (high) RPM Retention 47.06% RPM DROP
1.00 -- 61.73% (high) RPM Retention 38.27% RPM DROP

4l80/85
2.48
1.48 -- 59.68% (high) RPM Retention 40.32% RPM DROP
1.00 -- 67.57% (high) RPM Retention 32.43% RPM DROP


Headers 1 3/4 tube, sort of a mid length, with not much of a collector because of need to get ground clearance, it had to be shorten to transition to 3.0" oval pipe at firewall. Muffler are Billy Boat Z06 NPP Fusion for 3.0" for wide open 3.0" exhaust from header back when needed.



Air intake is home made cold air with dual 650 CFM filters feeding dual 3.0" piping stepped to 3 1/2' then to 4.0". MAF sensor used is LS2.

DSRE

iTrader: (7)

thats probably right with those headers and unlocked, i would have guessed 390-400 in a well optimised stick car, but what doesn't make sense is the rpm difference between your dyno run and gm's advertised hp peak, you might run it on a different dyno or at the track, and tune wise i'd want it much closer to 12.8-13.0, that thing is soft down low!

01midmetws6

iTrader: (1)

I have tuned a couple of LS376 motors and they are very soft on the base tune. Leaning out the AFR will help a ton. It also looks like the power dropped off at around 4400-4600, that might be caused by false knock pulling out a bunch of timing. GM has to tune them conservative due to different intake and exhaust configurations.

HioSSilver

iTrader: (8)

You need some 1 7/8 headers move the maf out a bit and a different intake tube set-up. I picked up tq, hp and response goin from a 1 3/4 header to a 1 7/8 on my stock ls6.

Kaane

iTrader: (2)

You need 8-12inches of straight tube in front of the MAF for it to read properly.

poorhousenext

With the help of another member with LS3 376/480 HO engine whose dyno sheet shows HP/TQ/AFR reading in 100 RPM increments, spotted why engine max HP peak didn't peak at about the same RPM as GM Engine Dyno sheet shows. Why it just looks like peak has moved.

His engine makes it Peak HP & TQ numbers about spot on with GM engine dyno 480 HO sheet. Looking at his AFR tells me why my engine looks like it making Peak power to/at 6500 RPM, it's not. It's that way because engine AFR is too Rich from 3000 RPM to 6000 RPM, then it leans out causing HP and TQ to increase above where HP should have peaked due to engine being to rich in peak HP RPM range. 6600 is about were HP would be as it falls off from cam's design real peak RPM...

The other LS3 376/480 engine's AFR is richer across the RPM range than my engine is. It's in the 9.0-11.0 range from 2500 to 6500 RPM. Mine is definitly too rich from 2500-6000, then from 6200-6600 AFR is probably close to being about right as GM's Engine Dyno Sheet reading is around 360-370 HP at 6500 RPM.








Like tws6 posted AFR needs looking at first, then depending on results and my desire to squeez out all the power out of the engine I can, air intake setup. Exhaust wise, I'm probably stuck with what I have. Would require custom fabed 1 7/8" headers and because of transmission size and lack of ground clearance, long tubes with merge collector can not be fitted. Had to modify 1 3/4" long tube headers that are on the car to fit.

Thanks to all, an especially to member who shared his dyno sheet with me. That helped both of us.

DSRE

iTrader: (7)

wow that things FAT! that can cause a Plethora of problems, i am surprised they continued the pull that out of tune!

poorhousenext

Update on LS3 480 HP Hot Cam.

Most of the feedback on why my engines numbers where down was correct. It's amazing how well it performed in 1/4 with the limiting factors I built into feeding it air.

At LS Fest I got to take car down the strip. 12.03 ET, 117.93 MPH, 1.96 60' foot time. Lack of Traction was not part of problem with 60' time. Didn't even spin the tires, but bent the rear end torque arm on 1st run, and a little more on second one because of how well car hooked up. By the way, car has 50/50 weight distribution. With fuel as run, it's 129 lbs heavier on rear. Approximate weight with driver was 3625-3650 lbs.



Because car was so close to running in 11's I've decided to try and get car in the 11.2 to 11.5 range even if I can't get 60' time in the 1.6 range but stay in 1.9's instead. Converter is stalled at 2800 RPM for a reason and I want have it restalled just to try and get 60' time down.

Below is what happened by swapping LS2 MAf out with LS3 style one. Notice how that change TQ curve. Notice also that at 5225 RPM peak TQ and HP were are nearly the same. Peak HP stayed at 360 and peaked at same RPM as before change. That means I need to modify intake air tube so that the two 3.0" tubes merge to feed 4.0" tube feeding throttlebody or change out tubes for 4.0" ones. Will be a coupe of months before I can work on getting that done.

Before MAF change.



After MAF change.



Here is the reason why I want car to run solid mid 11's. It's because it was built to dirve. It is not a show car, just a Pro Touring one.

dhctss

iTrader: (3)

Beatiful car man

6D9

iTrader: (1)

Car looks incredible!

04BlackGmc

iTrader: (19)

I just dynoed the 480 ls3 crate motor today in a car I tuned
1 7/8 ARH LTs with no cats.
Made 441 corrected

25* of timing and 12.2 Afr

I always notice the ls3 motors like fatter afrs.

msmnick

iTrader: (1)

That corvette looks Incredible. Simply amazing looking car. I'm sure this thing puts the biggest smile on the drivers face.

redtan

iTrader: (5)

Nice looking intake, how did you fab up those pipes from 1 piece like that?

Bohnseye

Can you tell me the brand and name of wheels on Vette? We are loking for a set like those for a 57 chevy two door post.

Thanks beautiful car

gmorris

Sorry, are you just blindly changing MAF sensors to see what the effect is or are you logging and tuning as well? Changing sensors will make a drastic difference in AFR and the tune needs to be adjusted for every intake change you make. The richness is just due to scaling issues on the MAF most likely.

poorhousenext

No, I never do anything blindly. Tune and data log.

In fact with only MAF change to LS3/LS7 one, run consistently in High 11's with all the things I've done to hurt power. By the way on a Dynojet Dyno engine as tuned makes 409 RWHP. That's only a 15% drive train lost even with all the impediments to making power I've built in...

That's not realistic RWHP for an Automatic. I'm guessing 25% drive train loss of GM 480HP at crank is a lot closer to the truth. Set up with 1 7/8 long tubes, correct 4.0'" MAF tubing setup, etc probably only a 20% drive train loss, 384 RWHP on a Mustang Dyno...LOL

Any way, even with all built in impediments I got the car to run consistently in High 11's, with a best of 11.79 @ 118.9 MPH with a 1.918 60' on 300 Tread wear street tires, no DR's or Slicks, 355 Rear gear. I drive around the water box, pre-stage, wait for other Driver to do burnout...



I'm in process of doing a build I want to try and get in 10's, with less than 400 RWHP, of course I'll be tuning on a Mustang dyno to keep engine under 400 RWHP. Again trying to do this on 200 or higher Tread wear street tires, and a 3.50 Rear gear.

In case things don't work out, I'm hoping I'll still have a nice driver.

By the way I'm what you call OLD & Stupid, 72. I started out Young & Dumb.





PS: Pohnseye, I PM'ed maker of wheels used on car to you.

Jimbo1367

WOW. enough said. lol

alocker

iTrader: (10)

Nice car and 1/4 numbers. I think you could shave another .1-.2 off that 60' by tuning the chassis more.

poorhousenext

Here is what the chassis tune is with with and without driver weight after run 3564 LBs, without driver 3,339 LBs with less 1/4 tank of fuel. Car weighs 3400 lbs with approximately full tank of gas and no driver.

Try to run with 1/4 tank = 4-5 gallon of gas. As you can see car is tail heavy with or without me & and suspension is tuned so that weight on each rear tire is about the same with the 10 lb imbalance on the passengers side on rear with me in the car. Didn't worry with making front weight within 10 lbs of each other. Pain to tune suspension.

You tell me what you would do to tune the suspension to get .1 - .2 quicker.






The car is heavy due to power seats, 4L80E based TCI 6X trans, 150 + lbs of heat shielding and sound deadening from firewall back. Massive billet wheels, etc. Car was never built with drag racing in mind. it's really just a driver that I wondered if it could run in at least 12s with a cam that is dead at 5800 RPM rather than 6500 to 7000 RPM or better you drag racers use.

Re-stalling Torque converter would be the best thing I could do. Only around 1800 -2000 RPM stall & efficient STR. Trans has Paddle Shift option. Don't know if you have any understanding of what it takes to make paddle shifting work. High stall ratio is not one of them. I could probably have the converter re-stalled to 2800-3000 RPM. That change is the most lily change I could make to get 60 FT time down. Probably would hurt how long it takes to complete a shift from time paddle is pulled back and let go. It's milliseconds now. Not like a lot of paddle shift 4L autos that take .5 to 1.0 second to complete a shift due to converter stall.

Here is a bad example of how long it take to complete shifts. Have to listen close and by the way I wasn't driving or riding in car...LOL


Again I wasn't driving or riding in the other car, but you may be able to hear
1st to 2nd and 2nd to 3rd auto shifts.

2011grandsport

If i am not mistaken you were in Atlanta back at the end of May first of June for the Chevy High Performance Nationals. That Vette is beautiful and ran good too! I did not see you at LS Fest there were so many cars there this year.

FINE RIDE! Hey you ever come down to the gulf coast for Cruisin The Coast?
If not, try to come next year there was over 7500 cars registered this year.