L98 rear mount turbo setup?
Thread Starter
7th Gear
Joined: Aug 2008
Posts: 7
Likes: 0
From: Milton township ohio
L98 rear mount turbo setup?
Hey guys im trying to find some people that have used a rear mount turbo setup on a l98 c4. Im building a totaly custom kit but i cant find a straight answer on what turbo to use since alot of people dont have alot of experiance with rear mounts. I tryed calling sts but they will not tell me what turbo they use. The only thing i do know is that they use a t4 flange and a .81 ar turbine housing. I was thinking of using a t70 divided t4 housing with a.84 turbine and .70 ar compressor. I am only planning on running 4psi of boost for now until i build the bottom end. Does anyone know how much power a stock bottom end will handle on a l98?, its got 70k on it with a 6 speed stick. Any input would be great
Le Mans Master
Joined: May 1999
Posts: 6,518
Likes: 1,304
From: Windermere FL
I cannot answer your turbo question but I can vouch that 4lbs of boost on a stock L98 will not be a problem. I have been running that amount of boost for years. Seems that the head gaskets are the weakest link.
My main problem was that the dual intercooler setup on my P600B had too much plumbing to get a lot of boost - that and belt slip. But I got an extra 3 lbs just from getting rid of the intercoolers and all the associated plumbing and going with a meth injection system instead. Since you will have a long run to bring the air up from, you may have similar issues so get a turbo that can generate boost accordingly. In any event plan on doing something to cool the boost. Of course you will need a good tune too.
My main problem was that the dual intercooler setup on my P600B had too much plumbing to get a lot of boost - that and belt slip. But I got an extra 3 lbs just from getting rid of the intercoolers and all the associated plumbing and going with a meth injection system instead. Since you will have a long run to bring the air up from, you may have similar issues so get a turbo that can generate boost accordingly. In any event plan on doing something to cool the boost. Of course you will need a good tune too.
Safety Car
Joined: Apr 2001
Posts: 3,525
Likes: 2
From: Houston TX
Way back when I had stock bottom end, I ran 8.5 psi for a long time without issues. It was fully tuned.
As many find, I thought if 8 feels good, what would more feel like. I had already maxed the pulley arrangement, so I tried a bypass on the IC (and related piping) and found that you can get 12 psi.
But, not for long, as it lifted the ring lands on several pistons. Granted, I had a lot of other bolt-on parts on the engine and was over 500WHP (running low 11s), so the lifted ring lands were probably long overdue.
As many find, I thought if 8 feels good, what would more feel like. I had already maxed the pulley arrangement, so I tried a bypass on the IC (and related piping) and found that you can get 12 psi.
But, not for long, as it lifted the ring lands on several pistons. Granted, I had a lot of other bolt-on parts on the engine and was over 500WHP (running low 11s), so the lifted ring lands were probably long overdue.
Thread Starter
7th Gear
Joined: Aug 2008
Posts: 7
Likes: 0
From: Milton township ohio
Thanks for the info. The mods that are done to my car are efi connection 24x ls1 computer swap, ls2 coils, comp 276hr cam, tpis mini ram, 1.6 roller rockers, arp head bolts, new felpro blue head gaskets, twin 58tb, ported and pillished stock 113 heads with comp duel springs and manley valves, spec stage 3 clutch, 12lb billet flywheel, totaly stock bottom end and full dyno tune. 347whp and 384wtq. Just want to throw about 4-5psi at it to get around another 100hp. I did not plan on running a intercooler due to the 8 or 9ft of piping that i figuerd would cool the charge. Maybe i should look into a small intercooler? I am just very unsure of the compressor housing size to use on the charger.
