Originally Posted by turbodog
Can someone please offer a convincing technical explaination of why you would need a tune when installing an aftermarket downpipe. From what i have seen personally, the only difference is that reduced backpressure may result in difficulty with boost control, which can be fixed without a tune. I read for a while and ol / cl delay was mentioned. Please advise.
I am curious about your thought process... what advantage to you believe an aftermarket downpipe gives that justifies a workaround, as opposed to tuning for the downpipe and reaping the normal stage2 rewards?
My first mod to my LGT was to gut my stock downpipe. The second mod was to gut my uppipe. I "noticed" a difference, and a dyno said I made 230 or so AWHP... puny and insignificant for the work those actions took. Within two weeks I had a Cobb DP on and Stg2 AP tune... now THAT made a difference worth the effort and money. I still got great MPG, but the car became alive with response and power.
If you have no interest in stage2, and tuning, you can get some gains out of merely gutting your stock downpipe... which is a snap to do, taking less than an hour.
I don't think merely changing the pill will do what you believe. Different pills change the rate of boost development, but don't limit it, per se. And, if you chose an aftermarket downpipe without a cat, even directly connecting your compressor to the WG would still likely result in overboost under certain circumstances. Retention of the mid-pipe cat would mitigate, but not eliminate, such boost creep under all conditions. Removal of both cats would certainly be an issue. Maintaining both cats would help, but again begs the question: why the AM DP.
You better have the means and inclination to maintain continuous touch with your ECU via logging. That goes without saying with even the simplest of mods, but especially those that may cost a motor.