I will have my stealth ram, AFR 195cc heads, and my 230/236 Comp Cam installed within the next two weeks. My current setup is in the sig, and the prom I have now is decently tuned for it. I was told before that before firing up the new setup, I should cut all VE values from 400 to 1600 RPM by 20 percent. Is this all I need to do?? I want it to be able to be safe to run and drive without fear of damaging my motor. Anyone?? Thanks in advance.

 

That would cause you to run leaner. While you VE MAY be "less efficient" at lower RPMs, I would still want to error on the side of richness with a new setup, not leaness. I would say ADD 20% first, and then tune from their.

FYI, below 2,500 rpm my Miniram (I only swapped the intake and heads, nothing else) needed a LOT more fuel than the stock TPI setup. The Miniram was a lot more efficient (which matched the increase torque experienced).

This was surprising to me because almost all the 'airchair experts' said I would loose my bottom end torque. But actual experience shows the opposite to be true. Luckily, I didn't cut fuel from VE tables but I still triggered a couple of "Lean O2 Sensor" SES codes when I initially began my eprom tuning.

 

I would definitely cut all the values by at least 20% from 400 up to about 1000. On a NEW engine you don't want to run rich and wash the cylinders with fuel. That's a bad thing. And - from personal experience ... when going from a stock type cam to a 230 degree cam the lower VE table needs to be modified heavily in terms of dropping fuel.

I think its actually cautious to CUT fuel in cases like this. Too much fuel on a new engine is bad. You KNOW that the new cam will be less volumetrically efficient ... so, you KNOW you'll have to cut fuel. The question is HOW MUCH fuel. 20% is in the ballpark for that cam compared to your old one. My 230 cam as compared to my STOCK cam is 50% different

Tim

 

Thanks for the replies. What about beyond 1000 RPM, will I be okay running it the way it is now?? And just to clear things up, the block/pistons etc. are not brand new, they have about 5,000 miles on them. Thanks.

 

I'm not tpi, but my motor as compared to stock TBI motor looks like this for VE. As you can see I don't get equal fuel (compared to stock) until 3000rpm, And you've got a higher performance motor than me, but your motor wasn't stock. Maybe this would give you a ball park guess.

 

wouldn't it be easier to reduce the BPW than run negative ve. i keep wondering if this is the cuase of driveability problems in TBI vehicles ?? the ecm is supposed to be scalling up not down. mabye the codes getting funky ????

 

Is it negative VE or does he just have the TunerCat COMPARE function active?

Tim

 

Sorry guys, the compare function is on, also I do have a reduced BPW of 121 from 135. So I guess the VE table I posted isn't really a good representation of my actual fuel.