racecar

I asked the same question months ago and got input to check AFR, add timing, change fuel injectors, and a lot of questions about electronic throttal control. All that is good, and now I have HPtuners so I am logging good data. With a 233/239 .600 lift cam and 11.5 to 1 compression, this thing should bark, but it is still sluggish. It has good power at WOT and it idles and runs good, just doesn't have good response. It's like a really hot motor with a carb and an accelerator pump that is not working.
I know that it is not the electronic throttal because I drove my freinds 06 LS7, that thing has quick revs. OK it's a totally different motor, but it is quick.
My motor should have quick revs, it is slow, any ideas???

DanO

Do you have a wideband O2 sensor? Fuel pressure sensor?

Start by logging some transient data. I.e. what does the Air fuel ratio do, what does the fuel pressure do, etc.. when you go to wide open throttle. Because if its not air, fuel, or spark.. then you have mechanical problems.

Xtnct00WS6

iTrader: (8)

Make sure ur tps is showing 100% when at WOT.

ArcticZ28

iTrader: (14)

What's your DCR? DCR dictates crisp throttle response more than SCR does. You could have 12.1:1 SCR but if your cam bleeds a lot of compression off with a lot of overlap or improper valve events, then you'll never have good response. Not saying it's necessarily the case, just something to look into if you haven't.

jimmyblue

iTrader: (11)

There are two throttle position values on the
electric throttle cars, and one interesting thing
to look at, is how the real blade position (I don't
remember the name) follows the pedal. This will
show you if the throttle opening is being held
back or if you can give it all the air it wants, and
it can't do anything with it.

If you have a big cam and a steep VE profile w/
RPM, you could be hitting a burst knock trigger if
the car has that enabled; seen this really hold a
'99 truck back, cable throttle even. More advance
at part throttle makes the motor snappier, have
you ever gone through the exercise of making a
ping limited spark table, all across the map? Do
you know whether you have reasonable spark
advance?

ArcticZ28

iTrader: (14)

Sorry to interrupt, but what is this burst knock jimmy? Does that have anything to do with hesitation right after a shift and clutch engagement?

ringram

Burst knock is the pcm's way of preventing KR on fast TPS Delta (it looks at airflow changes over time). Basically takes timing away so you dont go into knock. Its pretty rubbish and you are normally better off zeroing it out.
I think you should log timing as mentioned to see how it tracks the HO table. You might also want to log spark modifiers to see if anything is pulling timing like the aforementioned BKR demon.
Its worth playing with the throttle follower a little as well, that makes a difference with throttle response.
But my vote is for timing to be the issue. A cam engine will require a lot more timing at idle and just off due to inefficient fueling at low rpm. In my case I went from around 20 to 28* to address the issue.

RedHardSupra

iTrader: (1)

throttle response i find to get better mostly with VE nailed, and then proper timing (if it needs to be adjusted quite a bit from stockish settings). all the bucking, hesitation, surging that people mention so often in this forum, are just signs of these ve/spark being off.

BIRDONNOS

iTrader: (3)

hey fellas same problem with the t-rex, i logged the runs and also have a wideband. from idle the car seems to bog alittle and the a/f goes lean for a split second, it also does this when i am rolling (m6) and i stab the gas for a rev with the clutch pushed in, a/f goes lean for a split second then all is well, i believe this is the problem any way to correct this? i am running a maf.

racecar

AFR logs really good, about 13.7 cruising, and 12.7 at WOT. Fuel pressure is 58 with the car sitting still, have not logged any at speed. TPS is 100% on the scan data. Timing is 25 at WOT without knock, and 25 at anything over
3000rpm. That's all I can use without knocking. Have scanned on the track and adjusted many times. CR is 11.5 static and 9.3 DCR that should be quick. Just sitting in the driveway and revving the gas, there is a delay in the response. This makes it hard to heel and toe downshift when racing, I need to rap the gas quick as I am shifting and it just is not there. I'll check out the throttal body to make sure it is moving fast when I pop the gas pedal.

ringram

You need to look at the lower values in your table for off the line spark, Unless you leave at WOT all the time?

Also Mr Trex man, try SD mode rather than Maf mode does it feel any better? Maf wont work to well with a beefy cam near idle. It cant read airflow very well with the reversion occuring. Better yet, if you have efilive try OS5 with alpha-n fueling. That will give superb throttle response with larger cams.

GuitsBoy

iTrader: (4)

HA! So youre chasing this too...

patSS/00

iTrader: (6)

I'm also interested in this burst knock thing. Which burst knock table are we talking about? And does this only pull timing when knock is actually detected, or is it like a preventive thing that always pulls a set amount when throttle is opened quickly?

Bink

Burst knock is preventative. It pulls timing according to the table.

Burst Knock table is there to prevent Tip-in knock.