changing tune for an N/A intake and throttle body

**SgtMarshal** · 11-19-2015

I have a 2001 GTP. I installed an xp cam with 130 lb springs with a full size intercooler and a northstar tb with LQ4 maf. I decided to switch to a turbo, so im taking the intercooler off and swapping to an N/A L36 intake manifold with an L36 tb and maf. I also have 42 lb injectors. I'm changing the intake because the supercharger lim has been ported too much to seal to the supercharger and I'm switching to a turbo anyway, so I would like to be able to keep driving the car until the turbo goes on.

Can I just reset the tune to an N/A tune with a different IFR for the 42's?

Would I be able to get more timing advance than the normal N/A tune?

What would be a better way to do it?

**04lss** · 11-19-2015

If you're running an l67 lower end the NA tune is going to be geared for higher compression than you have.

**Fivefingerdeathpunch** · 11-19-2015

Just make the injector tables right and load the a stock maf table, tune the car from there.

**BillBoost37** · 11-19-2015

I'll add in that you are going to need to plug a set of injector holes.
L67 are in the heads
L36 are in the LIM

**SgtMarshal** · 11-19-2015

Originally Posted by BillBoost37

I'll add in that you are going to need to plug a set of injector holes.
L67 are in the heads
L36 are in the LIM

I'm either going to tap in some threads or use freeze plugs

**BillBoost37** · 11-19-2015

I'd want something more secure than a freeze plug when you are talking about crazy turbo builds that may get upwards of 15psi

**SgtMarshal** · 11-19-2015

Originally Posted by BillBoost37

I'd want something more secure than a freeze plug when you are talking about crazy turbo builds that may get upwards of 15psi

that's a good point, I hadn't considered it would be a factor. I'll just tap some threads and install some plugs then.

**BillBoost37** · 11-19-2015

Or.. get six nozzles for NOS and install them in those holes.

**SgtMarshal** · 11-20-2015

those nozzles are expensive, I think I would have to get a reducer from 3/8's to 1/8. I haven't tapped the holes yet so im not entirely sure what size tap I will use, but I think its about a 3/8's inch.

any idea how much timing advance I will be able to run with an N/A upper intake and an L67 bottom with an XP cam?

**CrazyGuy03** · 11-20-2015

Without boost, just reference a n/a timing table. And add from
there
with boost, probably less then what you had with the supercharger.

**J57ltr** · 11-20-2015

Originally Posted by SgtMarshal

those nozzles are expensive, I think I would have to get a reducer from 3/8's to 1/8. I haven't tapped the holes yet so im not entirely sure what size tap I will use, but I think its about a 3/8's inch.

any idea how much timing advance I will be able to run with an N/A upper intake and an L67 bottom with an XP cam?

3/8" NPT is a little large the hole is just over 1/2" for the tap, 1/4" NPT would be a better choice and 3/8-1/4 NPT reducer bushings are easy to find even at Home Depot.

Jeff

**SgtMarshal** · 11-22-2015

Originally Posted by J57ltr

3/8" NPT is a little large the hole is just over 1/2" for the tap, 1/4" NPT would be a better choice and 3/8-1/4 NPT reducer bushings are easy to find even at Home Depot.

Jeff

that would explain why I smoothed down the bottom 3 threads of the tap. I found someone that might be able to tig weld the manifold, which will be a lot easier than tapping and threading. If the welding part doesn't work out, I have a friend that has more tools than I, that will help tap the holes and plug them.

**J57ltr** · 11-22-2015

Tapping and plugging is the way to go it's easy. Trying to weld an aluminum intake of unknown metallurgy is asking for it to crack, even if you preheat it and properly cool it. Trust me on tapping I just had to change a 1/4 NPT to 3/8" NPT and it took me all of 5 minutes.

where the cable comes out in the picture, we only had 3/8" cord grips so that's where it was drilled and retapped.

Jeff

**SgtMarshal** · 11-23-2015

what size drill did you use to bore the hole out for the 3/8" npt tap?

**J57ltr** · 11-23-2015

Well, I think I used a 27 or 29/64", but it's really not that important. You want to look at where you want the bushing to set. Then use a drill smaller than that diameter. Since its tapered you can have it go in and stop within a few threads, or go all the way to the base. But if you go with the minimum size you have to ream a lot more metal out. I don't keep track I just grab a drill bit that's just larger than the tip, at the first few real threads on the tap.

The chart calls for a 37/64" (.578", or little bigger than 5/8") for 3/8" pipe and for 1/4" 7/16".

Jeff

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