C5samuelt

Alright so I spent months getting this motor right. Zo6 ls6 engine everything bottom end is forged stage 4 cam, ported heads (243s) big *** torque converter 525cc injectors 58lbs. I only made 358 wheel just scraped 400 crank, the tuner was in shock as similar builds as mine came in making over 410-420 to the wheel. Motor wouldn’t go past 358wheel spent 8 hours at faster proms tuning it with no luck what could be my issue why did I get such a low number is the dyno numbers reading wrong? I mean took it for a spin today wheels don’t catch at all it’s quick as **** instant torque it’s unbelievable feels more then 358Wheel horsepower and I’m just wondering what this could be if the dyno is right or it wasn’t reading right, also like to add the the motor redlined at 7100 rpm which is crazy scary to me for it to push that far just on one single pull.

Eshoremd

Can you post the graph?

NSFW

Some dynos read high, some dynos read low. My car made 450 on one and 475 on another with no changes to the car.

Have you seen numbers of a build similar to yours on the same dyno? Not just the same make/model, but at the same shop.

Does the dyno chart include an AFR plot? That might provide a hint, if it's way off.

A couple ideas to confirm that the engine is healthy: a compression test is pretty straightforward, other than the cylinder next the brake booster. Use a heat gun to confirm that all of the headers are roughly the same temperature range. You'll probably need an automotive one as you can easily get beyond the range of the ones intended for consumer / indoor use.

Purple92

There are literally dozens of potential causes for the engine not making the power that you "expected".

Diagnosing the issue is not going to be easy, but the details of the dyno runs may give you a clue. What kind of Air / Fuel Ratio were you seeing at WOT ??? Was the timing advance where the tuner would have expected it to be ?

I'd start by doing a simple compression test, and if ANYTHING looks amiss, do a leakdown test. That should verify the health of the motor itself. Then maybe try running at a different dyno facility, and see if the numbers are close.

Just to give you something to think about - assuming the engine is mechanically OK, some possible causes:

Fuel Supply system not able to supply enough fuel
Restricted exhaust system
Fuel Injectors not operating properly
Bad Coil(s) / Plugs / Wires
Improperly installed camshaft / Improperly Ground Cam
Slipping transmission
PCM not functioning properly
Bad Knock Sensor(s)
Throttle Not Opening Fully
Insufficient Valve Springs

NSFW

Great idea. This would be easy to verify with a data logger. Or if you don't trust the data logger, just remove the air filter/bridge and watch the throttle open and close with the engine off.

Speaking of logging... It might also be interesting to do a dyno pull and watch RPM, MAF (grams/second), ignition timing, ignition retard, intake air temp, and coolant temp. If the temps are high enough, or if the knock sensors hear knock, the engine will retard timing, which will cost power.

Mr. Black

Big *** torque converters and dynos don't always play well with each other.

grubinski

I had some compromised plug wires once on the dyno that cost me 90 horsepower… I never felt it on the street because I’d been behaving myself until after the dyno.

phils C5 vette

That's a rough one after all your work and your just above making stock power after a rebuilt.
Yes, the stall will steal some power and can make for an ugly dyno graph, but your tuner is known for turning off too many trouble codes and maxing your misfire tables which will make it even more difficult to diagnose why your power level is low.

Its doesnt sound like all 8 cylinders are firing.

benflynn

Do a virtual dyno or a pull, dyno numbers mean as little when they are low as my sooper high one does. Back it up with more data. G/s is a good hint at hp too

also what was the trans temps looking like? Fluid still red, slipping trans will eat up some hp

jfigus

There are some online calculators that convert air flow to HP. It's purely theoretical. But if you use HP Tuners and monitor the mass airflow sensor you can convert that to theoretical horsepower. It's just another measurement to sanity check your engine power output. But it's not going to be an accurate measurement of HP.

Did you tuner check for knock detection. Knock will pull a lot of timing and kill power. I had a bad knock sensor and the tuner disabled it when tuning on the dyno. He couldn't make big power with the knock sensor enabled.

benflynn

Good point, I just ran into bad or incorrect sensors really, pulling like 10 degrees, knocks the power right out.

G/S won’t tell u what power it makes but about what it should.

NSFW

It's all about getting as much information as you can about what's going on in the engine. MAF, AFR, temperatures, ignition advance, ignition retard, etc, etc.

Some of them will be about what you'd expect, and that helps rule out some potential issues.

Some of them will be outside the expected range, and that gives you hints about what's not right.

C5samuelt

so this is all I have one dyno run with picture second one made an extra 10hp and torque stayed the same and yes I’ve seen similar builds of mine make 410-420hp to the wheels

C5samuelt

C5samuelt

so here’s the thing the tuner said the motor was beyond perfect he couldn’t get anything else out of it which to me didn’t make sense I do have some knock sensor codes don’t know if that shows anything but here’s the dyno sheet also to add I am running an oil cooler and a trans cooler from hayden rapid cool, temps were very Suprisingly good after multiple pulls on the dyno

C5samuelt

ok so after searching for a while saw people posting some dyno sheets (at the same tuner) one that stood out was 2 basically stock ls1’s with a stage 3 cam and 3200 stall converter stock bottom end stock heads no machine work done to them, one made 380Wheel one made 386Wheel, yes I did a compression test everything came out perfect, we ran a heat gun at the tuners and they all came out pretty much similar temperatures don’t know if that’s good or bad, here is the dyno sheet since a lot of u are asking

Purple92

The ruler flat Air Fuel Ratio curve on the bottom part of the dyno run is suspicious. It's almost unheard of to get something that consistent.

If it were me - I'd be thinking of getting another dyno run - Somewhere Else !

C5MSG2004Vert

Are the knock sensor codes current of historical. A bad knock sensor will cause the pcm to pull timing. So that could cause a horsepower loss. In any case, if you have a bad knock sensor you should fix it, unless they are tuned out.

C5samuelt

it’s a current code comes on when I floor it and goes away when I normal drive it so I’m assuming it needs replacing which is a bummer but I’m putting a fast 92mm intake manifold on it later this week so while I’m down there they getting replaced but it makes sense

C5samuelt

I’ll take it to power tech whose right by faster proms later this week to get a run in see if there’s any difference