I have ran a number of turbos on my truck and am almost ready to go twins. I am trying to decide which ones to use. I had a 57/65/14 S300 and then went to the 64/71/14, as well as running the stocker. I am wondering how much if any will my spool slow down when I add the twins. So I am considering running one of three S300's but do not want terrible spool up. Basically I am really happy with the 64/71/14 but if the spool was slower once added to a set of twins then I would go to a smaller comp wheel like the 62mm. I will be using a Garret GT4202(non ball bearing) based turbo with the S300 in my twins.

This will be on the 1990 truck.

 

I think the 57mm turbo would probably work well with the 4202. Probably be a faster spooling setup, with the smaller comp and turbine wheels.

 

I can go bigger on the larger charger. I have a couple trucks and may buy another so the gt4202 can get used on another truck if needed.

I'm not looking for twin recomendations so much as what people have noticed going from a turbo they were using as a single to using the same turbo in their twin set-up. Basically does your system spool as fast with the turbo in twin form as it did when you only ran it as a single.

The way I see it is you should still spool the small turbo almost the same and then your big turbo spools to back it up. I'm just not sure if pulling the air through the large turbos compressor will slow down the small charger to where it seems laggy. I know its kind of a strange question but I know a lot of you guys have ran say, 62/71/14's then upgraded to twins and used it as your smaller turbo so let me know if the spool is now higher up in the RPM's.

 

Rule of thumb is that spoolup will be slightly slower in twins vs the same turbo as a single. The 4202 is a good spooling primary though. If you still have both S300s the physical size of the two secondaries is similar so you can try one and swap it out for another if you don't like it. I am going to bet you like the 57mm better.
I am thinking about a 57mm/gt4202 twins set too.

 

Thanks man thats the info I was looking for. I dont have the 57mm laying around currently but I may have one again soon. Anyone else have experience with this?