LT4 Dyno LT4 run's! (what's wrong...)

[Peer81]

Hello everybody,

My name is Peter and i have a question,
The 96 LT4 vette is from a friend of mine! He bought the vette from Rogers and had it shipped to the Netherlands.

Problem with the goverment for automobiels (or how do you call it in the us) They didn't have a 96 vette with handgears in the centrale computer so no road clearance for this vette!.. But with a German clearance (legal bypass so to say! )it wasn't a problem in the Netherlands anymore, luckely for him! But thats another story...
The Vette was for sale at Rogers and the engine didn't run for over a year (he and therefor i was told) The car has a mod list:

Six Speed LT-4 330 Horsepower Grand Sport Engine
Extensive, Quality Performance Enhancements By Vinci High Performance Including Custom LT-4 Power Package and Custom Power Package Which Includes Modified PowerFlo Thermostat and Constant Monitor Fan Package To Ensure Cooler Engine Temperatures, VHP Performance Computer Upgrade Package, Calibrated To Enhance Performance and Reliability, Underdrive Power Pulley Package, VHP Air Intake Package, 52mm Throttle Body With Air Foil, Low Restriction Corsa Exhaust System, VHP Billet Aluminum Adjustable Fuel Pressure Regulator, Ported, Polished, Bench Flowed Heads, VHP Fiberglass Wrapped Headers, Honed Intake Manifold and Port Match To VHP Cylinder Heads, Motorvac Fuel System, Ripper Shifter Kit, Skip Shift Eliminator, Taylor Plugwire Harness, R&R Flywheel and Clutch Assembly, New Waterpump and Distributor, 4.10 Rear End Gear Ratio-Performance

So a big amount of stuff is from http://www.vincihiperformance.com/index2.htm
Overthere we don't know anything about vinci.... what are the reaction's on there mod's...?

And this is the dynosheet with 2 run's from last week (no air/fuel sheet..)

His and my question is, we think this LT4 could run better numbers then the 325HP and 442Nm, what do you think?
Rogers sayed the enige has around 400HP (don't know if thats block of rear wheels)

Second question, when you look at the second run (dark blue) the torque curve has a weird push from 2200 till 3900rpm, and the torque and hp (ofcourse) have some weird pieks and fall's from 5000 till 6000rpm.
Do you know what the problem could be (we didn't make any more runs) Because the first runs is very smouth and the second is a bit messy, could it be an enginecomputer glitch? Sensors? Some after results for this engine not running for over a year? We don't know... Did somebody over here have some similar problems or could you point a direction?
We didn't check fuelpressure of change it (this is the first time i see it standing in the list :t)

Well, that's about it for now, hope to hear some reply's soon!

Greetings Peter.

 

[twiget]

325hp does seem a little low for that list of mods, but there is only so much the bolt-ons can do. At that point it sounds like the car needed some time on the dyno to tune it, and tweak the computer program.

Rogers claim of 400hp is probably BHP. With the accepted 15% drive train loss of the C4's that puts the expected hp at 340. The dyno results do seem to indicate a loss of power somewere, but tune the engine some, and who knows.

Jason

 

[CKA_Racing]

Ah, the Netherlands. I was there once in in the 1990's. Business trip to The Hague installing a network/computers for the United States War Tribunal when the Aeron building was being converted into the court and jail.

400hp minus 17% for drive train lost turns out to be 332hp at the wheels. So the dyno results are not far off at all. It all depends on what type of work was done on the heads. Also the camshaft counts for alot. What type of cam specs etc.

Bluewasp has a modified LT4 Grand Sport that has 350-360 RWHP. All Lingenfelter parts. But again it all depends on what stage heads were installed and how radical of a cam was installed.

Some are better than others when it comes to tuning the computer. You could gain power just by having an expert tune it.
I know they should have been able to program it which they seem to have done a good job of. But you may be able to get a little more out of it.

 

[Peer81]

Hee Steve, nice to hear you where in the Netherlands some time back. Had a good time? The Hague is just a 40 minute drive from me and if i'm correct this Vette is currently making the streets onsave in that neighbourhood!

Well if it's just 10 hp then it isn't such a big deal, but getting the max out of this LT4 is always fun!

But what can be changed to a LT4 to improve torque/hp?
I have a 81 so most of the stuff can be done by hand but in my idea's a LT4 is almost compleetly computerstuff...
With the original Airpump in place it isn't possible to get a good reading on the air/fuel ratio or am i wrong?
(i'm also reading this topic: http://corvetteactioncenter.com/forums/showthread.php?s=&threadid=35117)
So a Datamaster could get some good info on readout's on a LT4 (and other +91 engine's) Is it also possible to changes some settings from the ECM or just monitor?
And what is the best part in the engine to search for more hp (without changing the hardware!). It would help if we could get some info from Vinci aswell offcourse, for spec's on the cam and heads..
And nobody an idea on the second weird pull?

I see Bluewasp live's in Germany? Well, that's close by for your standards offcourse Hope to see his GS once if it's in Germany!

Greets Peter.

 

[Michael Malone Smith]

Hi Peer81...........looked at that car myself back in the spring. Maybe getting a hold of Vinci might help. web....vincihiperformance.com
email..info@vincihighperformance.com
tech phone..407-292-4500


Hope this will help you guys,I thought that was a heck of a car

 

[Robert lt4]

@Peer Thanks for opening this topic!

Well I am the (proud) owner of this car. A second lookon the HP's is not bad at all. But I also believe that it could (should) be more. The thing thats really bothering me are the "spikes" at the end. This in combination with some occasional vibrations makes me wonder (worry) a bit.

Comming month the Vette will have its maintenance because last 12 months the car did not run much. I e-mailed the dyno sheet to a company here in Amsterdam and we will do some additional (dyno) testing after the maintenance. I also mailed it to Vince. The problem with Vince is that they do not respond.......

I am open for any suggestions and other input.



Robert

 

[all4c4lt4]

I would think with the headers, exhaust, and head/intake work you should have more than 325 rwhp. I agree that your dyno sheet "spikes" in some places, but overall isn't that bad. You should definately change your cam to take full advantage of the head/exhaust/intake mods. I would think you could obtain at least 30 rwhp from a good cam given your current setup. I am not an expert when it comes to tuning or analyzing dyno graphs, but you could also try posting on www.corvetteforum.com tech section. There are many over there who understand tuning the obdII. Good luck with reaching vinci...hopefully some others here can chime in too...

 

[stumpy]

Yea yea yea the hp looks a bit low but who cares, look at all that wonderful torque. HP is what you brag about but torque is what wins the race! You should be very pleased with those #s. I bet it's a beast on the road.

As for the rough ending, this is not an expert opinion but it looks like it may have leaned out. Did you get AF ratios? If so then send it to your tuner for a PCM adjustment.

 

[Peer81]

Sorry but HP is messured from Torque, so if one stayes behind the other one is aswel. But that isn't the prob, they're just great numbers no doubt about that!

I think there wasn't a AF ratio for this vette, but i don't know for sure. Could check it offcourse.
Thankx for the info everyone!

Greets Peter.

 

[stumpy]

Sorry but HP is messured from Torque, so if one stayes behind the other one is aswel.

True, but HP is based upon the application of tq over time. So if you just want to be quicker than the other guy, drag racing, then you got great numbers. If you want to out run them on the road then you want hp.

However, given that the numbers are so far apart, could it be that your clutch is weak? Perhaps it's slipping at high revs and skewing the hp results. The stock clutch is not supposed to be that strong. I already smoked mine on it's 6th run down the 1/4 mile by getting it too hot.

 

[Peer81]

Thankx for the info Stumpy!

The car isn't mine, i'm just living on the internet compared to Robert (the owner) .

The more hints we have for this problem the better offcourse, what Robert is going to do with his vette i don't know.
You body off is taking alot of my time now...

Greets Peter.

 

[stumpy]

One other option to verify hp is to calculate it based upon weight and trap speed in the 1/4 mile. Take it to the track, weight it on the scale with the driver to get race weight, then get a few good runs in. Take the weight and 1/4 mph to smokemup.com math calculator and see what it says your hp comes up to. Many believe this to be more accurate than a dyno. It seems to be right on for my 96 Impala SS.

BTW, you in Amsterdam? I need to get back there to do some more window shopping.

 

[Shriker]

Couple things to consider. First , you only revved it to 6K and LT4's especially modded like that one can make more power over 6k , even with that mild stock cam- and the graph appears to still be climbing mildly. Secondly , the car has 4.10 gears which will show ~5-10 rwhp LESS than the stock gears (3.45's ) would have. Something was wrong on the second pull with the bumpy line, could be alot of things from ignition to wires to plugs to computer etc. Most likely just a glitch because of the nice first pull.

It is VERY odd that Vinci (dont know much about them) basically a top end job (heads/cam/intake exhaust) but did NOT do a CAM. The stocker is very mild, something like a LT4 Hot Cam is still relatively mild and would add at LEAST 25 rwhp to that car.

Anyway, I'll bet if you dyno it on a good day again (be sure you have good fuel in there as well)and let it rev you may see 330-35 rwhp and adding 5-10 for the gears gets you nearly to 350.

Hope that helps.....oh , and nice ride.....