I have the mods in the sig, how much if at all is it holding the car back? Should I get a 58mm or is that overkill and the 52 would be fine?.

Here is what the heads flowed

2 135/101
.3 190/134
.4 236/161
.5 267/180
.6 269/188

 

You are probly fine with the stock but if you are going to upgrade 52MM is the biggest I've heard you should have for an A4 and a 58MM for an M6. I don't know why though.

 

Your stock TB will be good up to about 400rwhp. I think you are still OK!

 

Hmmm, idk about that, my friend put down around 415 hp with his 383 on a 52 mm i think and it was pulling vacume so he bought a mono-blade.

 

These numbers are probably correct, but i will say this. I just finished installing a BBK58mm TB and put in some 30# injectors. I don't know if it was the combo of the two or what but it pulls much harder up top than before.

 

Were you running stock injectors with the mods in you sig? If so they may have been maxed out and running lean on the top end. Also if your PCM was reprogramed to reflect the injectors, you are getting gains from the better programing.


A stock TB will flow about 650CFM, more than enough for most mild to moderate heads/cam set-ups. A 52MM TB will flow about 750CFM, this enough for almost any setup unless you are spraying the motor. Unless your blown you will never need a mono blabe.

The A$ cars are more prone to idle and drivability problems arising from larger TBs, so many beleive it's best to not go too big.

 

is it holding you back...technically yes.

i'm sure you'd pick up a couple hp by going to a 52mm TB.

i guess it depends on if you consider 5hp being "held back"...and worth the extra $400 or $200 for a ported stocker.

 

I just looked at my datalog, at WOT i am about 90 kpa on the MAP reading, I have read that this is one way to tell if there is a restriction in the intake, it should be 98-100. Any trueth to that?

Also i am going to the track tonite, my friend has a bored out stock tb to 52mm that i can borrow, would i need tuning to run this, just to try it out at the track for the night?

 

I think you are at the point where a 52mm will net you some gain and for just the one night go ahead and borrow your friends.


The risk to A4s from a larger TB without tuning comes from normal driving not WOT and even so a few miles wouldn't hurt a thing so if others with a$ cars want to try something like this go for it.

 

It isn't the MAP's absolute number that matters (it will vary depending upon the weather, your elevation, etc), it's the drop. If the datalog says the barometric pressure was 92 KPA, you're golded. If it was 102, you have some serious restriction. Make sense?