So my tuner tuned my car on SD without the intake pipe, will putting a 3.5 inch intake pipe mess up the tune?

stock evo 8 9.8 hotside turbo btw

 

Put it on, log afr's and fuel trims and pay attention to its manners. If it drives poorly, runs AFR's that are different from before, or your fuel trims get all crazy then you need a retune. I wouldn't expect it to be a problem though.

 

i agree with biggie... i wouldnt expect it to be a problem.

 

It's speed density, it won't matter..

 

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it could change the boost a little tho....

 

Which a speed density tune will compensate for...lol.

 

ANYTHING that causes a change in VE will effect the SD tune. By how much? Marginal to negligible? Maybe so.

 

That is correct!!

 

Is that why a properly done SD tune can be run at 20 or 35 psi and be fine?

The intake pipe doesn't effect an SD tune. Just like a boost leak or a charge pipe blowing off doesn't effect it.

 

Please clarify that you're telling me an intake pipe doesnt effect the VE of an engine? I'll welcome a discussion as I'm very open minded!

 

Specifically the reason a car with blown off intercooler piping runs ok, is because you are using a MAP sensor in the intake manifold. Assuming you have a good seal between the intake manifold and head at that point(danger to manifold), the engine is acting as NA , running in cells on your fueling map and timing map that corresponds to the actual MAP and rpm. But consider you arrived at that VE by having the compressor and intercooler piping connected probably using part throttle. Throttle position can have effects on pumping efficiency too!.

The reason the maf that cannot run with blown off piping is obviously the MAF is passing air not going to the engine making it super rich.

Also consider the SD car with blown piping is still pushing air against a turbine, but now that turbine does not have a compressor building pressure in the intake manifold. Different VE for those gasses to exit through that turbine when its freewheeling(besides the point but I've tuned WOT at ambient pressure by taking piping apart; this will get you in the ball park but is NOT exact) .

Again consider placing a 2" intake on a 35r turbo. Tune the car SD. Take that 2" tube off and put the 4" intake on. You betting any change in VE at a given rpm vs boost? I'm thinking a lot higher VE with the 4" tube.

these are all situations where ve changes. SD is not all it cracked up to be in so many other scenarios except minor boost leaks appearing. Well.. and you can get off the freeway when an ic pipe goes boom!