Any Advice for increasing spool time, REAR mount

**JAX04** · 07-09-2010, 03:54 AM

Ok, Does anyone have any advice on timing down low for increasing spool time on a rearmount turbo.

Yes, i know the obvious, move it up front. Well, im not doing that. lol

ive been told that if retard the timing down low, i will increase cylinder pressure etc. without building torque, which will help spool the turbo.

If this is the case, where is a good place to start, and how far into the rpm should i take this.

I have a built 4l60 with a 3200 stall. So i was thinking i should try this up to my stall speed atleast...???

any thoughts??

thanks,
kyle

**Cutlass** · 07-10-2010, 07:13 PM

Yeah I've talked to my turbo buddy about this in the past. you can get a faster spool by retarding the timing during the spooling rpm. you can also get faster spool with a leaner A/F ratio.
The leaner AF burns hotter and faster then a rich mixture. Hot and fast exhaust makes a turbo spool faster. But you definitely want to richen up the AF in the higher RPMs.

Retarded timing causes the gas and air mixture to burn later and is wasted out the exhaust rather then used in the engine to build the max amount of cylinder pressure to push the piston down. that wasted exhaust helps spool faster.

Thats about how I remember him describing it anyways. I don't have the hands on experience like he does but what he said seems to make sense.

**sama lama** · 07-28-2010, 07:11 PM

A friend of mine has a rear twin turbos on his c5 corvette my idea was to get stainless exhaust and thermal rap all the way to the turbos. It should help keep the velocity up inside the exhaust tubing.

**Cutlass** · 07-28-2010, 07:30 PM

This conversation came up again yesterday at work. He no longer believe retarding the timing to get a faster turbo spool is a good idea. He describes it as zero gain. You taking away from the engine's horsepower by retarding the timing so any gain you get from faster spool is basically nullified.

**JoshuaGrooms83** · 01-21-2013, 06:15 PM

any update on this other then keeping stock manifolds and wrapping everything? and what it seems on stock 5.7s a .81 ar helps alot

**JoshuaGrooms83** · 12-05-2013, 06:28 AM

well for updates if you having already, I myself have experienced some decent spooling even with a T76 .96 AR and long tube headers

Wrap from the headers all the way to the turbo. wrap an extra layer aroung the headers to the ypipe merge to keep that pipe nice and warm. Also a stall and longer gears help too. Keeping the gears in the 3.08 or lower range will help it spool up.