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Help with disappointing dyno results

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Old 07-02-2018, 02:40 PM
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fast.asleep
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Default Help with disappointing dyno results

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 kmís (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 Iíve heard on the forums I think something is wrong. If anyone has any words of advice please chime in
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Old 07-02-2018, 03:03 PM
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TheBlaster9001
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Originally Posted by fast.asleep View Post
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 kmís (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 Iíve heard on the forums I think something is wrong. If anyone has any words of advice please chime in
The hard starting should be tuned out. Mine started hard, then really hard after long tube headers. I got into tuning, and had that fixed right away.

You have a blower on top of all the other mods? The mods alone I would figure 300 whp. What does fuel pressure do when you are doing a dyno run? What size injectors do you have?

This could be a tuning issue. Hard to tell.
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Old 07-02-2018, 03:11 PM
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fast.asleep
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No blower yet I wanted a before and after comparison. After fixing a vacuum leak on the intake the car needed to be retuned. Not sure what the fuel pressure was on the dyno but when the key is on (engine off) it’s at 40psi. At idle fuel pressure goes to 50psi
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Old 07-02-2018, 03:18 PM
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TheBlaster9001
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Originally Posted by fast.asleep View Post
No blower yet I wanted a before and after comparison. After fixing a vacuum leak on the intake the car needed to be retuned. Not sure what the fuel pressure was on the dyno but when the key is on (engine off) itís at 40psi. At idle fuel pressure goes to 50psi
Gotcha. I am hesitant to say so, but I think this may be a tuning issue. Unless there is something drastically wrong (misfiring, valves not lashed/hanging open), I would expect a little more out of your setup.
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Old 07-02-2018, 03:19 PM
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Dt86
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What fuel injectors do you have? I have similar mods, minus the heads, and am running Bosch 3 24lb hr injectors. I also began tuning and it makes a big difference. Just changing the injector size and full throttle power enrichment was noticeable.
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Old 07-02-2018, 03:41 PM
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fast.asleep
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Stock fuel injectors.
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Old 07-02-2018, 04:28 PM
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Originally Posted by fast.asleep View Post
Stock fuel injectors.
There's a chance that might be your problem. Do you have datalogs from your pulls? How high does the injector duty cycle get?
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Old 07-02-2018, 04:40 PM
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Originally Posted by fast.asleep View Post
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 kmís (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 Iíve heard on the forums I think something is wrong. If anyone has any words of advice please chime in
Attach a dyno sheet. The hard starting and surging can and should be tuned out, it probably needs more cranking fuel and open loop fuel.
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Old 07-02-2018, 05:12 PM
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How low is the compression ratio?
How much torque and where is peak torque and hp?

Last edited by ddahlgren; 07-02-2018 at 05:14 PM.
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Old 07-02-2018, 05:31 PM
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Compression? I want to say stock. As for peak hp and torque:


Originally Posted by bjankuski View Post
Attach a dyno sheet.


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Old 07-02-2018, 05:52 PM
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856SPEED
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Itís easy....you are running a choking intake system....that base and runner do nothing over the stock long runner set up...makes torque, not horsepower....mini ram will provide about 40 rwhp over that....with the same time tune....after a tune ....even better....ask me how I know!!

surprised itís not making more rwtrq though.

Last edited by 856SPEED; 07-02-2018 at 05:55 PM.
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Old 07-02-2018, 06:21 PM
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elaborate on high flow base?

You need the right sized injectros and a good tune thats holding you back big time.
Look up Wongs Performance in Vancouver
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Old 07-02-2018, 06:22 PM
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..... 250 rear wheel hp is actually a nice improvement over stock rated 240 flywheel hp … small-ish heads , small cam , TPI and Long tubes got you 50-60hp over stock ! … nothing wrong with that ! …..
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Old 07-02-2018, 06:24 PM
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Is the chip custom tuned for this camshaft
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Old 07-02-2018, 06:28 PM
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Originally Posted by 856SPEED View Post
Itís easy....you are running a choking intake system....that base and runner do nothing over the stock long runner set up...makes torque, not horsepower....mini ram will provide about 40 rwhp over that....with the same time tune....after a tune ....even better....ask me how I know!!

surprised itís not making more rwtrq though.
if a cam, heads and longtubes gives me 50 hp, I canít see an intake giving me 40.

Originally Posted by vader86 View Post
Is the chip custom tuned for this camshaft
yup. That was the cam that was in it during the dyno tune
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Old 07-02-2018, 06:33 PM
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….. What size are the combustion chambers on those heads ? ….. And , what year is your car ? …..

Last edited by C409; 07-02-2018 at 06:37 PM.
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Old 07-02-2018, 06:38 PM
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Originally Posted by C409 View Post
….. What size are the combustion chambers on those heads ? …..
They started at 65 but I had a machine shop bring them down to 58 or 59. It’s a 1987 l98

Last edited by fast.asleep; 07-02-2018 at 06:39 PM.
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Old 07-02-2018, 06:48 PM
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Originally Posted by cuisinartvette View Post
elaborate on high flow base?

You need the right sized injectros and a good tune thats holding you back big time.
Look up Wongs Performance in Vancouver
Edelbrock high flow base. AFAIK it is the same as the TPIS/ACCEL base

What do you reccomend as far as injectors? I have to swap them out anyway when I move to a blower
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Old 07-02-2018, 07:15 PM
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Originally Posted by C409 View Post
..... 250 rear wheel hp is actually a nice improvement over stock rated 240 flywheel hp Ö small-ish heads , small cam , TPI and Long tubes got you 50-60hp over stock ! Ö nothing wrong with that ! Ö..
What timing are you running?
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Old 07-02-2018, 09:52 PM
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Originally Posted by 383vett View Post
What timing are you running?
comp specs 4* advance so that’s what the builder did. The guy that put it together is very competent but it was his first time tuning an OBD1 car.


Last edited by fast.asleep; 07-02-2018 at 10:00 PM.
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