Bad dyno =(
Bad dyno =( Guys I had the most depressing dyno runs today.
little bit about the car.
had a vortech SC on a forged 383 complete setup.
blew the heads and then came the light rebuild.
removed the SC.
new heads with great porting,
new gaskets and everythign else checked ok.
so slapped heads on w new gaskets of course.
ran a compression checked all checked perfect.
So we have a 383 full forged internals.
stock ported heads with heavy springs, roller rockers, hardened pushrods.
52mm TB, port matched intake
MSD opti., msd wires, w wire mgmt.
CAI, MAF w/ screens.
42 lb/hr inj.
headers, no cats, 3" to flowmaster
alum flywheel, SPEC clutch.
M6
So I thought we should have about 400HP to the wheels min.
NOT! dyno came up with 266hp 316 Tq.
im like what the hell happened.
car responds well and doesnt hesitate.
my question is will tuning make up some serious diff like im expecting?
are my expectations reasonable?
im very disappointed, any help recommendations are appreciated.
im proablably gonna look for a tuner any recommendations?
I have Tunercat and have logs of the dyno runs w Datamaster.
dont know much about programming tables but im getting the hang of it.
any help is appreciated....
Thanks.... Joel
little bit about the car.
had a vortech SC on a forged 383 complete setup.
blew the heads and then came the light rebuild.
removed the SC.
new heads with great porting,
new gaskets and everythign else checked ok.
so slapped heads on w new gaskets of course.
ran a compression checked all checked perfect.
So we have a 383 full forged internals.
stock ported heads with heavy springs, roller rockers, hardened pushrods.
52mm TB, port matched intake
MSD opti., msd wires, w wire mgmt.
CAI, MAF w/ screens.
42 lb/hr inj.
headers, no cats, 3" to flowmaster
alum flywheel, SPEC clutch.
M6
So I thought we should have about 400HP to the wheels min.
NOT! dyno came up with 266hp 316 Tq.
im like what the hell happened.
car responds well and doesnt hesitate.
my question is will tuning make up some serious diff like im expecting?
are my expectations reasonable?
im very disappointed, any help recommendations are appreciated.
im proablably gonna look for a tuner any recommendations?
I have Tunercat and have logs of the dyno runs w Datamaster.
dont know much about programming tables but im getting the hang of it.
any help is appreciated....
Thanks.... Joel
Last edited by dually681; Nov 2, 2013 at 07:22 PM. Reason: more setup info
TECH Apprentice
Joined: May 2009
Posts: 323
Likes: 2
From: NW AR
Hopefully your engine was spec'd for boost, especially the piston rings. Also screw dynos, get a decent run down the drag strip will tell you your rear wheel HP. Hell I can tell when something is up on my car when I see 1-2 MPH difference in the 1/4 mile.
it does have a very aggressive CompCams cam.
with boost it had on dyno 550hp and 580tq
but that was then.
now i have no SC, its in the garage, but im thinking of putting it back on as the tune was perfect with it.
Now im having trouble i guess because of the tune has to be modified and im making some progress but not much.
did i mention it drives well.
but it just doesnt have that kick u in the butt feel.
it has torque,,,,,,,
with boost it had on dyno 550hp and 580tq
but that was then.
now i have no SC, its in the garage, but im thinking of putting it back on as the tune was perfect with it.
Now im having trouble i guess because of the tune has to be modified and im making some progress but not much.
did i mention it drives well.
but it just doesnt have that kick u in the butt feel.
it has torque,,,,,,,
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So you basically had a 383 built to handle a supercharger and you took the supercharger off and are running N/A now?
If so, I'm sure you compression is way too low to make impressive power N/A.
If the cam you have was spec'd with a blower in mind it's not ideal for N/A.
You didn't mention if the car is an M6 or A4 and what the rear gear is. If the car is an A4 and you had a converter for the blower application it will not be correct now due to you changing now much and where the engine makes power and torque.
If you haven't changed the tune much from where the supercharged engine was it is sure to be way off. Have you had a wideband on it to see what the A/F ratio is?
If so, I'm sure you compression is way too low to make impressive power N/A.
If the cam you have was spec'd with a blower in mind it's not ideal for N/A.
You didn't mention if the car is an M6 or A4 and what the rear gear is. If the car is an A4 and you had a converter for the blower application it will not be correct now due to you changing now much and where the engine makes power and torque.
If you haven't changed the tune much from where the supercharged engine was it is sure to be way off. Have you had a wideband on it to see what the A/F ratio is?
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And ill bet your compression is like 9:1 since it was built for boost. Your running a boost tune NA it's doing exactly as it should. Add compression and retune. And what's the "very aggressive comp cam"? Is it a cc305 that's usually speced for blower applications?
I have seen cases where boost cars will make a VERY low number on the dyno because the dyno did not load the engine properly and the pcm just got confused and the car wouldn't make any sort of reasonable number, one guy had a 400rwhp slip for a 9 second full weight Impala. He had it tuned well on track but with the single BAR MAP and such the pcm just couldn't make it work right on the dyno
That said NA I don't believe you will get a problem that severe. It is true that a dyno will never tell the whole story but at the same time I don't believe it will give you a 260hp reading on a 400rwhp NA car. If the timing is still real low for boost that would be a lot of power left on the table but I don't think you are going to get 140hp from tuning alone an if the tune was that far off I would worry about damage.
That said NA I don't believe you will get a problem that severe. It is true that a dyno will never tell the whole story but at the same time I don't believe it will give you a 260hp reading on a 400rwhp NA car. If the timing is still real low for boost that would be a lot of power left on the table but I don't think you are going to get 140hp from tuning alone an if the tune was that far off I would worry about damage.
Could be retarded timing, too low compression, too rich, or a combination of all of those.
Can't just yank a supercharger off an engine and run it without it an expect good numbers. You need to datalog it and see what all the sensors are seeing.
Can't just yank a supercharger off an engine and run it without it an expect good numbers. You need to datalog it and see what all the sensors are seeing.
I have seen cases where boost cars will make a VERY low number on the dyno because the dyno did not load the engine properly and the pcm just got confused and the car wouldn't make any sort of reasonable number, one guy had a 400rwhp slip for a 9 second full weight Impala. He had it tuned well on track but with the single BAR MAP and such the pcm just couldn't make it work right on the dyno
That said NA I don't believe you will get a problem that severe. It is true that a dyno will never tell the whole story but at the same time I don't believe it will give you a 260hp reading on a 400rwhp NA car. If the timing is still real low for boost that would be a lot of power left on the table but I don't think you are going to get 140hp from tuning alone an if the tune was that far off I would worry about damage.
That said NA I don't believe you will get a problem that severe. It is true that a dyno will never tell the whole story but at the same time I don't believe it will give you a 260hp reading on a 400rwhp NA car. If the timing is still real low for boost that would be a lot of power left on the table but I don't think you are going to get 140hp from tuning alone an if the tune was that far off I would worry about damage.
What he said ^^
And what he said ^^
Chances are that you have three major issues at play:
1. Your static compression ratio is way too low for a N/A application;
2. Your "very aggressive cam" drops your dynamic compression to a point where your engine will NEVER make the power it should;
3. You tune is way off.
You are either gonna have to reinstall the supercharger and retune the PCM.....or.....you are gonna have to take the engine apart and look at installing some pistons (to increase compression) that are more compatable with a N/A application.
Now....before going any further, how about answering these questions:
a. What is your current static compression ratio;
b. What are the specs of your cam;
c. What are the specs of your heads;
d. What is your engine's quench?
The answers to those four questions will TRULY pave your 'way ahead' as far as getting your engine "right".
KW
1. Your static compression ratio is way too low for a N/A application;
2. Your "very aggressive cam" drops your dynamic compression to a point where your engine will NEVER make the power it should;
3. You tune is way off.
You are either gonna have to reinstall the supercharger and retune the PCM.....or.....you are gonna have to take the engine apart and look at installing some pistons (to increase compression) that are more compatable with a N/A application.
Now....before going any further, how about answering these questions:
a. What is your current static compression ratio;
b. What are the specs of your cam;
c. What are the specs of your heads;
d. What is your engine's quench?
The answers to those four questions will TRULY pave your 'way ahead' as far as getting your engine "right".
KW
Tire spin test doesn't mean much, if the tires are old and hard they spin easily compared to even if the same tire were new.
Far as cam specs, you never know what people will call a "blower cam" many companies do not differentiate blower vs. turbo cams even though they should, and who knows about compression you could have a reasonably built blower LT1 with compression in the mid 9s or one of the stupidly built ones down in the 8s.
What were the results of the compression test? Cranking compression might give us some ideas about the static compression and cam.
Far as cam specs, you never know what people will call a "blower cam" many companies do not differentiate blower vs. turbo cams even though they should, and who knows about compression you could have a reasonably built blower LT1 with compression in the mid 9s or one of the stupidly built ones down in the 8s.
What were the results of the compression test? Cranking compression might give us some ideas about the static compression and cam.