I'm having an impossible time getting my pump settings to where the car transitions smoothly on and off throttle. First off, I have tuned lots of cars with the microtech including my old setup with the renisis, I know the basics. I have tried everything I could think of and I can't shake this hesitation when getting on throttle lightly or immediately after shifting. The issue happens in vacuum so it's not a staging issue. The car goes way lean unless I feed the throttle extremely slowly or abruptly which makes it less noticeable. Even changed the primaries from 720 to 2000cc since it runs on E85 and I thought maybe the smaller ones didn't have enough juice but it's doing the same thing with the larger ones.

Here's the setup

BRE engine large street port 76mm open throttle into bre uim
2000cc primaries
1680+ 720cc secondaries
E85
40psi fuel pressure while at idle
Lt10s

I have tried everything and increasing the pump amt % and pulse helped. Lowering the trigger seemed to help also but unsure. Based on my prior experience it seems as though I need to increase the % to higher than the maximum of 99%.

Right now these are the pump settings:

Pump1
Amt 99%
Pulse 12
Trigger 05
Stop 2psi

Pump 2
Start 3500
Amt 99%
Pulse 12
Trigger 05
Stop 3psi

Problems are happening before 3500 so it probably doesn't have anything to do with pump 2 as I haven't tuned there yet. It feels like the amount should go to higher and the pulse down to about 10 since once it bogs lean it goes slightly rich before leveling off.

Any help is appreciated.

Thanks

Chris

 

are you 100% sure is not a staging issue ?? 720 to 2000 is big. whats your % ??

 

Hi,

Im not using 720 anymore. I switched to 2000cc primaries because I thought exactly what you are saying. Regardless, my old setup had 720 primaries and I didnt have any issues. Its happening in vacuum when staging isnt happening. Right now the car has 6 injectors, 2 2000cc primaries and 2 720 + 2 1680

Im only going from 2000cc to 2400cc during staging...

Chris

 

Bump!

 

Anyone?

 

I'm wondering if you're low base fuel pressure has anything to do with it. I used to run 40psi base, but my car ran better with 50+. (on e85)

 

did you have the same throttle body on the other setups? I've seen a lot of setups with single butterfly setups and they are always a major pita to get it transitioning smoothly.

 

do you have the map line close to the tb?

 

The problem is the throttle body.

Switch your pump settings from MAP to TPS and tune from there. You'll need a lot more fuel than with the factory staged throttle body. Primary port velocity is in the toilet with these large throttle bodies.