loss of high end power

bob brady

3 black cars
last summer my car's dyno pull produced 446 rwhp and 633 rwt. this winter i added 60 lb injectors, precision slic, beefed up transmission, and et streets. recently i had a dyno pull that produced 380 rwhp and 479 rwt. technician said the power dropped off at 4900 rpm, yet last years run pulled to 5750!! i doubt it's the valve springs because i have only driven the car 200 to 300 miles. on the road at wot it seems to strain at the end of second, begging for a shift! when it finally does hit third, it pulls much stronger, same as it does in the beginning of second! any ideas?
 

Royal-T-Ltd

Well-Known Member
last summer my car's dyno pull produced 446 rwhp and 633 rwt. this winter i added 60 lb injectors, precision slic, beefed up transmission, and et streets. recently i had a dyno pull that produced 380 rwhp and 479 rwt. technician said the power dropped off at 4900 rpm, yet last years run pulled to 5750!! i doubt it's the valve springs because i have only driven the car 200 to 300 miles. on the road at wot it seems to strain at the end of second, begging for a shift! when it finally does hit third, it pulls much stronger, same as it does in the beginning of second! any ideas?

Do you have any logs? I could guess, but too many different scenarios - my guess is it’s running rich .... but without any data it’s pointless. Did the dyno tech hook up a Wideband?


Sent from my iPhone using Tapatalk Pro
 

salvageV6

Daily Driver
Was the dyno. set up the same?

Car set up the same chip and tune/boost level wise?

What was done in the transmission/converter, that would be my guess... shift point change internals etc.

You should post up the graphs and any info. you may have for temps. etc. and logs etc. if you have them.

If not we will just be guessing.
 

bob brady

3 black cars
chip came with 60 lb injectors from turbo tweak. 26 lbs boost 10.80 a/f ratio. i turned my alcohol up to 6.5, too high?
 

bison

Moderator
Staff member
5750. Was that engine somewhat modified? Most stock headed LC2 will fall off a cliff around 5000rpm. If it has stock heads and a stage 3 turbine or smaller and less than 30psi power will be dropping after 5000rpm. Never rising. The stock engine with mild modifications and lager turbo will typically be strongest between 4100 and 4500.
 

bob brady

3 black cars
Was the dyno. set up the same?

Car set up the same chip and tune/boost level wise?

What was done in the transmission/converter, that would be my guess... shift point change internals etc.

You should post up the graphs and any info. you may have for temps. etc. and logs etc. if you have them.

If not we will just be guessing.
car was held in 3rd gear. 2800 stall converter and transmission from
5750. Was that engine somewhat modified? Most stock headed LC2 will fall off a cliff around 5000rpm. If it has stock heads and a stage 3 turbine or smaller and less than 30psi power will be dropping after 5000rpm. Never rising. The stock engine with mild modifications and lager turbo will typically be strongest between 4100 and 4500.
5750. Was that engine somewhat modified? Most stock headed LC2 will fall off a cliff around 5000rpm. If it has stock heads and a stage 3 turbine or smaller and less than 30psi power will be dropping after 5000rpm. Never rising. The stock engine with mild modifications and lager turbo will typically be strongest between 4100 and 4500.
5750. Was that engine somewhat modified? Most stock headed LC2 will fall off a cliff around 5000rpm. If it has stock heads and a stage 3 turbine or smaller and less than 30psi power will be dropping after 5000rpm. Never rising. The stock engine with mild modifications and lager turbo will typically be strongest between 4100 and 4500.
stock block and heads. te44, alky, 60 lb injectors with matching chip, 26 lbs of boost, plus all the small stuff,
 

bob brady

3 black cars
Was the dyno. set up the same?

Car set up the same chip and tune/boost level wise?

What was done in the transmission/converter, that would be my guess... shift point change internals etc.

You should post up the graphs and any info. you may have for temps. etc. and logs etc. if you have them.

If not we will just be guessing.
car was held in 3rd gear. 2800 stall converter and transmission from Dave Husek
 

Fat Nat

Well-Known Member
446 rwhp with a te44 and stock heads??? Was this on the same dyno both times and were you there for all of the pulls to watch what the cars doing. Plenty of factors play in to dyno numbers. Hell was the conv locked
 

bob brady

3 black cars
446 rwhp with a te44 and stock heads??? Was this on the same dyno both times and were you there for all of the pulls to watch what the cars doing. Plenty of factors play in to dyno numbers. Hell was the conv locked
yes, same dyno, i was there to watch, and the converter was locked.
 

bob brady

3 black cars
yes, same dyno, i was there to watch, and the converter was locked.
i was questioning the torque (663) which was waaay over the horsepower!. you can feel the car lay down at the end of second, and when it shifts to third it pulls much harder.
 

Mike T

Well-Known Member
Not to dispute the results of the first dyno pull but the numbers of the second pull seem to be more accurate (proportion wise).

Below are a few shots of a pull from some years ago with similar HP to yours. Ported heads, decent cam and springs. It was totally done by 5300 and more realistically about 5100. Point being it made the same HP as yours with less RPM and far less torque so something seems to be askew mathematically with the first pull. Do you have the graphs?





dyno baseline.png
powerlogger dyno 443 hp screenshot.png
 
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