What timing are you running?
Help with disappointing dyno results
Safety Car
Joined: Aug 2009
Posts: 3,752
Likes: 276
From: Melbourne, Victoria, Australia
I recently had the car tuned on a dyno prior to a blower but the dyno results were seriously disappointing. I can feel an improvement over stock but not ads much as I thought.
It only made 250 rear wheel hp!!!
The car starts hard (I expected this since we removed the 9th injector) and surges on cold start up but the surge goes away as it warms up.
My mods are:
Engine:
80000 km’s (aprox 50k miles)
Stock bottom end
AFR 180 eliminator heads
Comp 268 xfi hr13 ( duration @50 218/224)
High flow L98 base, ported SLP runners, ported plenum
Adjustable fuel pressure regulator
Exhaust:
Long tube headers
True dual exhaust
Magnaflow mufflers
Transmission:
700r4
2400 stall torque converter
Shift kit
Considering everything I’ve heard on the forums I think something is wrong. If anyone has any words of advice please chime in
It only made 250 rear wheel hp!!!
The car starts hard (I expected this since we removed the 9th injector) and surges on cold start up but the surge goes away as it warms up.
My mods are:
Engine:
80000 km’s (aprox 50k miles)
Stock bottom end
AFR 180 eliminator heads
Comp 268 xfi hr13 ( duration @50 218/224)
High flow L98 base, ported SLP runners, ported plenum
Adjustable fuel pressure regulator
Exhaust:
Long tube headers
True dual exhaust
Magnaflow mufflers
Transmission:
700r4
2400 stall torque converter
Shift kit
Considering everything I’ve heard on the forums I think something is wrong. If anyone has any words of advice please chime in
How old is the fuel pump and fuel filter?
I would start looking at replacing the fuel filter, standard the fuel pressure should be 40psi.
The TPI loves 50 to 60 psi fuel pressure, not sure on the camshaft.
The car should run good, I got my 85 from std mid 14 sec quarters to 13.2 sec quarter mile with minor works using standard cam and heads. Went to the blower after that..
Cold air intake long tube headers a tune up, cut air filter lid and adjustable fuel pressure regulator..
That is with street tires, so you should be able to get into mid twelve second quarters with what you have.
Try to no go overboard with a hot cam with TPI runners, go to a mini ram or super ram setup.
The std TPI runs out of breath at low rpm, you want to have a torque monster to accelerate from the line.
From idle to mid 5k rpm, anything else you are sacrificing torque and off the line launch.
That first gear is great to give you a launch, with a blower its all about torque so very mild cam suits best.
With all my mods the car ran good, easy start hot or cold.
Look into new 30lb injectors, and standard fuel limiting removal.
Check with fuel injector connection (FIC), they can help sort out your C4 -- make her fly.
https://fuelinjectorconnection.com/
Cheers
Last edited by gerardvg; Jul 2, 2018 at 11:00 PM.
Thread Starter
Instructor
Joined: Nov 2004
Posts: 211
Likes: 1
From: Calgary Alberta
Hi
How old is the fuel pump and fuel filter?
I would start looking at replacing the fuel filter, standard the fuel pressure should be 40psi.
The TPI loves 50 to 60 psi fuel pressure, and long tube headers.
You must use long tube headers to wake the L98, not sure on the cam
How old is the fuel pump and fuel filter?
I would start looking at replacing the fuel filter, standard the fuel pressure should be 40psi.
The TPI loves 50 to 60 psi fuel pressure, and long tube headers.
You must use long tube headers to wake the L98, not sure on the cam
Safety Car
Joined: Aug 2009
Posts: 3,752
Likes: 276
From: Melbourne, Victoria, Australia
Yeah look at replacing the fuel pump fuel filter and 30lb injectors, the standard fuel injectors can struggle with higher fuel pressure.
plus look at the FIC fuel injector tests, how poorly some flow just dribble a best.
Last edited by gerardvg; Jul 2, 2018 at 11:08 PM.
Melting Slicks
Joined: Apr 2007
Posts: 2,616
Likes: 111
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
New pump and injectors would not hurt anything. The a/f ratio looks reasonable but just the average of 1 bank so really don't know much beyond that. Ignition timing would be good to know if left stock or changed. Personally would have used more cylinder head and cam. over 30 year old injectors kind of silly to keep too.
Team Owner
Joined: Sep 2001
Posts: 62,160
Likes: 1,733
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Based on what youre saying, its only the injectors that seem like they could be going off if theres actually something 'wrong' with it at all. It may just be out of breath due to the intake.
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Melting Slicks
Joined: Apr 2007
Posts: 2,616
Likes: 111
Timing is another good point. My car likes a bunch of total timing at WOT at high RPM...makes the best power at 36 before TDC ....But that can be risky too depending on your thermostat and cooling system in general.
Team Owner
Joined: Sep 2001
Posts: 62,160
Likes: 1,733
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Depends how much boost you want to feed it. I considered a blower at some point and would've had the engine built for that compression and a fair amount of boost, I wouldn't run much boost on the stock bottom end.
Thread Starter
Instructor
Joined: Nov 2004
Posts: 211
Likes: 1
From: Calgary Alberta
Last edited by fast.asleep; Jul 3, 2018 at 07:38 PM.
Melting Slicks
Joined: Apr 2007
Posts: 2,616
Likes: 111
Having said all of that, I would not be too upset by your numbers. You have some torque at the tire off the stop light and overall it should be a fun car to drive.
Last edited by 856SPEED; Jul 4, 2018 at 07:47 AM.
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
I would want to see the knock counts if any at WOT as timing might be leaving something on the table. If none I would be tempted to move the timing up until on or two and if a bunch take some out as ECU might be pulling too much out.
Drifting
Joined: Jun 2018
Posts: 1,678
Likes: 229
From: Michigan
Testing a TPI all over 4600 RPMs is laughable. What they other guys are telling you about the intake making HP is simple. HP is the ability to make Toque at high RPMs. Your Heads/Cam are designed to make power Higher than the SLP Runners. It's not matched well.
As with anything mods, Data log and ensure health and function before getting too upset. Also, if your Cam... and I didn't look for any details here, is designed for a blower, don't expect it to add a lot NA. It will come alive under boost.
If you want HP a mini Ram or similar will be needed.
As with anything mods, Data log and ensure health and function before getting too upset. Also, if your Cam... and I didn't look for any details here, is designed for a blower, don't expect it to add a lot NA. It will come alive under boost.
If you want HP a mini Ram or similar will be needed.
Last edited by KyleF; Jul 9, 2018 at 01:47 PM.
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
hp=(torque X RPM)/5252
so hp is the rte you can generate torque.
No torque no hp.
Torque generally falls off 15% between peak torque and peak HP so bigger the torque number and the longer you can hang on to it the more HP.
This engine is only making 7 more HP between peak torque and peak HP it is basically a 245 HP engine and probably only has 245 worth of airflow.
The only chance for a low buck help might be 1.6 or 1.65 rockers to put some area under the curve for more air flow.
With the typical loss of 15 to 20% for rolling resistance trans u-joints tc. On it's best day this is a 380 to 395 ft.lbs and 280 to 300 HP at the flywheel.
This is about what you would expect from the intake and heads.
so hp is the rte you can generate torque.
No torque no hp.
Torque generally falls off 15% between peak torque and peak HP so bigger the torque number and the longer you can hang on to it the more HP.
This engine is only making 7 more HP between peak torque and peak HP it is basically a 245 HP engine and probably only has 245 worth of airflow.
The only chance for a low buck help might be 1.6 or 1.65 rockers to put some area under the curve for more air flow.
With the typical loss of 15 to 20% for rolling resistance trans u-joints tc. On it's best day this is a 380 to 395 ft.lbs and 280 to 300 HP at the flywheel.
This is about what you would expect from the intake and heads.
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
fair enough. Most of the stuff I have run on a dynojet are bikes and they get sensitive in how tight you strap them down or tire inflation. Would not have believed it if did not see it more than once on turbo busa's. Usually around peak torque when needs to tied down tighter to get a better bite on the roller. I have run hundreds if not thousands of engines though few on chassis dyno's. Hooking the car or bike up is generally more trouble than what is learned. They do in my experience work well for finding drive response and an ocassional miss that is hard to catch in a data stream though.
Last edited by ddahlgren; Jul 6, 2018 at 07:12 PM.
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
recent dyno on ls1 = 593 engine hp. Same engine in car made 492 whp, that was a manual tko 600 trans and ford 9 inch rear on a mustang dyno. 17% drive train loss. I do agree with you that the factory numbers read higher, more like 10% on a manual and 15% auto.