Retune when going with a bigger turbo??

[Willmartens]

Hey all, i'm changing my setup from an ebay gt35 t3 .63 ar to a precision 6266 T4 .81 Ar.
I talked with my tuner about getting a retune when going with a bigger turbo, and I was told that I won't need a retune. The tune was pretty dialed in (with a couple revisions) to run great on the ebay turbo. I always thought a retune is needed when going with a turbo that will flow a ton more air on the same boost level and spool a good deal later. Not doubting the tuner as he has been very helpful and I trust him, just looking for some more opinions! Can always just adjust the fuel map myself, but would prefer to not have to since I paid for a tune.

[JOutterbridge]

It should be retuned switching to a completely different turbine. The compressor wheels are similar but they won't spool up the same. Also you'll have more power so your top end WILL need adjustment unless you're tuned super rich already. It may drive fine on the street but I wouldn't trust it long term at all

[rajicase]

I went from a s256sx to a s366sxe on the same TRM tune. Maybe it wasn't smart, but it ran fine and pulled hard and didn't pop.

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And a 35r and a 6266 are a lot more similar than a 256 and a 366. Id be inclined to just run it and watch your AFRs. Bet itd be fine.

[328iFun]

Depends on your budget. If you have the time left on your tune then do it.

If you have the funds, then do it.

If your tuner guy tuned to a specific turbo then your not going to reap the entire benefit of your new setup. This is simple to understand.

What is not easy to understand is that a tuner doesn't wanna blow up your motor anymore than you do. So with reasonable sense they adjust fuel accordingly. Not only with mathematical factors in mind but hardware definicines in mind as well. That old saying, "it's not perfect unless I do it myself."

So yes, I would think that if you run a bit bigger turbo the 'safe' factors that a good tuner would put in place in fuel maps would run your bigger turbo decently at moderate or low boost safely.

Realistically though, if you plan to change your setup often. Just learn to tune the car yourself or go standalone

I figure that most 'known' tuners send a standard base map to all E36 cars based on the engine anyway. Who really knows though

[ba114]

Are you still MAF based? if so, in theory your tune will be "fine" provided the original tune had enough space in it's load axis to account for the increased airflow. Any decent tuner would not have tuned the final column(s) to the limit of your existing setup, allowing safety if you ever upped the power.

If you're not MAF based, then yes, you will need a retune.

[Willmartens]

Yes I am Maf based. Tune is good for around 1400 mg/stroke, way more than what I will be making. I am adding meth anyways so tune will have to be revised for that, just wanted to get it dialed on the new turbo before introducing meth. When I add meth, I think i'm going to leave the timing alone and just pull some fuel out of it, but still keep it fairly rich for added safety. Thanks for everyone's help

[ba114]

Yes I am Maf based. Tune is good for around 1400 mg/stroke, way more than what I will be making. I am adding meth anyways so tune will have to be revised for that, just wanted to get it dialed on the new turbo before introducing meth. When I add meth, I think i'm going to leave the timing alone and just pull some fuel out of it, but still keep it fairly rich for added safety. Thanks for everyone's help

That would be a waste. You can easily add timing when running meth, that's kind of the whole point!

[Willmartens]

That would be a waste. You can easily add timing when running meth, that's kind of the whole point!

Fully understand that I would get more gains by adding timing, but at the moment not really looking for much more power as my clutch is nearing the end of its life unfortunately. Later on I will forsure add some timing and turn her up