Rule of thumb help

[Kevin Doe]

I've got a cam only car now, and have tuned it myself with EFI Live. It currently runs great. I started with the stock tune, and over time honed it in to where its at now.

I am installing a set of stage 2.5 5.3 liter heads from Texas Speed (or PRC if you will). What is a good rule of thumb for the VE table increase. I was thinking if its related to the torque curve, then it would need to increase by the same percentage that the torque would increase. Would bumping the table up by 10% be a good starting point?

My setup is a 5.7l stock bottom end (with valve reliefs cut into the pistons), 11:1 CR, Stg. 2.5 5.3l heads, MS4 cam, 1 7/8" headers, dual 3.5" intake piping, dual 3" exhaust through a 3" x-pipe, LS6 manifold.

I've posted my most recent tune that I have no my work computer (its a COS3 tune file) for reference. The tune is a few days old, and I've made some updates to the custom calibrations but the VE table remains unchanged.

[SSpdDmon]

I'd give it 6% on the high end (i.e. the 105kPa column). :)

[Kevin Doe]

And you think the rest of the VE table will be close enough to be safe while I'm doing the Auto VE again? Looking at most of my WOT logs I only get into the 100 kPa column, hmmmm. Might be normal, I'll have to pay attention to what atmospheric pressure is sometime before I start the car.

[SSpdDmon]

And you think the rest of the VE table will be close enough to be safe while I'm doing the Auto VE again? Looking at most of my WOT logs I only get into the 100 kPa column, hmmmm. Might be normal, I'll have to pay attention to what atmospheric pressure is sometime before I start the car.
I would blend it in. Maybe do (from 2800rpm on up) 6% increase for 100 & 105kPa, 5.5% for 90 & 95kPa, 5% for 80 & 85kPa, and so forth. I'd bump up the cells under 2800 similarly, just not as much. As an added safety, you could try bumping down the initial commanded AFR at WOT to something a little richer like 12.5 or 12.2. If the car runs a little lean outside of PE, it won't be too hard on it as long as there's no crazy KR or something.

[WHYTRYZ06]

I would just re-do the whole autove process at a crusing speed on the highway, then I would use the IAT VE multiplier table A0014 to adjust for the varying IAT temps... much easier than hacking your ve table.. my .02 ....thats what i did when i make changes to my car...

[Kevin Doe]

I would just re-do the whole autove process at a crusing speed on the highway, then I would use the IAT VE multiplier table A0014 to adjust for the varying IAT temps... much easier than hacking your ve table.. my .02 ....thats what i did when i make changes to my car...

But the VE will have actually changed. I don't follow your logic.

[WHYTRYZ06]

But the VE will have actually changed. I don't follow your logic.

ok logic... very simple.. start over.. over and done. do u follow now? your ve will be fairly close to what u have now.,..

[Kevin Doe]

Well I know this. VE will be higher in most places than stock. A higher actual VE than what is in the table will cause a lean condition. Clearly that is bad. I was wanting to know about how much I should increase my table so I can start rich, and then work lean. Not the other way around (just starting from my current VE table). I think SSpeedomon answered my question though.

[WHYTRYZ06]

ok raise the whole ve by 5%..... done start from there

[Kevin Doe]

Thanks for the suggestions, but I cannot understand what you are trying to say...........

[WHYTRYZ06]

Thanks for the suggestions, but I cannot understand what you are trying to say...........

I tried... sorry, nothing more i can say....:welcome:

[ssvolvo]

You might cut the spark back just a tad on the top end unless you are using good gas. Those chambers are quite small.

Nice VE table Michelangelo...looks like a playboy centerfold. Mine looks like the cover of a rock climbing magazine!!!

Those heads are nice aren't they? I almost mounted them on the wall instead of on the car!

My Kpa only hits 100 also no matter how hard I try.

Good luck, John

[Kevin Doe]

Well I got everything all installed and ready to be tuned. Here is the modification map I developed to multiply to my previous VE table. Hope its a good makes a good starting point. I"m also going to change my commanded fuel to a bit richer, and bump the timing down a bit as well for the VE mapping.

Here is the modifcation map.
http://i93.photobucket.com/albums/l55/Kevin_Doe/RX-7/modifiedVEmap.jpg

[ssvolvo]

Kevin,
That looks like a good start. Looks like your done racing for the year with the weather and all huh?

Maybe just my setup, same heads as yours but only 220 duration cam, but Im only able to run 20 degrees spark at the strip with 93 octane gas. I don't have a catch can, could be why.

Take that thing out and BEAT IT!

John