Dodge SRT Viper Forums : ViperAlley banner

Best turbo size for 1200rwhp

7K views 30 replies 14 participants last post by  AndyMac 
#1 ·
Hi Guys, got tt gen2 (built engine,trans,diff, aem ecu) car is runnig on BW Turbos ( 67 mm) now is making around 900rwhp, one the turbos died last week,I want to make around 1100 to 1200 rwhp, but not sacrificie fast respond, dont get me wrong I know I'm gonna lose power on lower rpms and get some turbo lag,but maybe somebody already walk that road and can help me get the best turbo size for that power, I use the car for roll racing and some times for drag, thanks a lot for your help!!!! ( I use vp c16 thats the only race fuel I have around here, not intesting on pump gas).
 
#2 ·
You said you had 67mm turbos on there now, do you have any other specs? I assume you are talking about the compressor side. What size A/R exhaust housing are you running now?

With your goal being 1100-1200ish i'd look around at 76mm Turbos with a good hotside to flow enough but also not kill your spool time. You'll probably be in the .96 A/R hotside area to have good flow but also good response.
 
#4 · (Edited)
2001 viper gts.
Built engine(cp 8.5:1 pistons, oliver rods, billet main caps, valves,1.6 roker arms, 1300cc inyectors, etc)
Built trans, twin disck cluth
Upgrade Rear diff and unitrax axels
Aem ecu.

It appers that I've been running on diesel turbos from a LTA 10 cummis engine 😣😣😣, now I know why one is gone.

When I bought the car the specs the previous owner gave me were:

67 mm turbos on the compresor side, 81a.r on the hot side, dont know the a/r on the turbine, Even do the car makes 900rwhp at 12 psi.

The silver srt10 its paxton superchared thats my sweet baby jeje, but the gts is faster.
 

Attachments

#5 · (Edited)
You can get 1200rwhp out of Precision 6766 turbo's (as long as Twin Turbo). I am on stock bottom end, built top end motor and at 10psi at 867RWHP with 6766's and an SCT tuned on a very very safe tune and 93 gas. With your built motor and race gas you could throw more boost at it and get into the 1200rwhp with minimal turbo lag.
 
#6 ·
Pushing more boost out of the current turbos probably would net you the type of power you want. If they're on their way out though (leaking seals, shaft play) and you want to upgrade, you could get a larger turbos like the 76s with .81 a/r, or .96 a/r hotside if you want more top end power. You'll probably be able to keep a similar boost level or much lower than you would be running on the 67s to hit your goal. Keep in mind the larger the A/R the more lag time you'll have but the more it will flow overall making it easier to get the numbers you want provided the compressor can move enough air

.96 is the next logical size up from .81.

What rpm do you end up with full boost at now with .81 a/r hotsides? Also are they journal bearing or ball bearing?

Edit: those look like borg warner S300 turbos?
 
#7 ·
IMHO I would not boost smaller turbos up to 1200rwhp for one reason only - the bottom end and mid range TQ will be impossible to control without extensive boost control/tuning and traction control. It will have a much fatter curve than a larger twin turbo setup making the same peak power.

The larger turbos will cost you in bottom end and mid range - but if traction limited anyway, it is easier to control the top end. It will also be more efficient under boost/have less backpressure.

If you had a 4-5L V8 I'd stay smaller, but you have over 8L NA and even some 76's will pull 5lb by 3k - so traction is your big issue. In short, 1200rwhp from a set of 67's will have too much TQ where you can't use it, the larger units will give the wheels more chance to catch up/keep up

I could be wrong.. and boy I have been
 
#8 ·
What torque said. I ran the precision 6766s journal bearing up to the 1000 range and it was completely uncontrollable pedal wise. came on like something branded it's ass with a hot iron. it would start to take off, then just instantly spin nuts....even say 3/4 throttle in 4th gear rolling it would get to about 2000 rpm and just go sideways. I'd say bigger, at least 76s. but honestly if you are chasing, or intend to at some point go bigger than the 1200 you want, you are going to need larger anyway. biggest problem with ours are space to put them.

either way, good luck and keep us posted.
 
#9 ·
biggest problem with ours are space to put them.
This ^^

Hotside not so much but compressor cover for sure.... I just purchased a set of T67 Turbos with .81 A/R Hot sides for a lower boost setup on my 2001 and the biggest issue i saw was the compressor cover. Anything s-trim cover wise or larger with a 4" inlet will be a tight fit or might not fit easily unless the exhaust piping into the turbo is setup correctly to accommodate for it. I ended up going with a smaller compressor cover with 3" inlet instead.

Not trying to hijack the thread, but figure its on topic somewhat
Anyone happen to have pictures of phsyical supports for their turbos or how they managed to mount them? Would be nice to see some different setups. Im about to start fabbing up some "mid pipes" between the stock headers and turbos and im looking for ideas or pitfalls to avoid.
 
#10 · (Edited)
Got it guys, so 67's vs 76's, with my current set up I was between 2600 rpms and 2900 rpms full boost, those are journal.

I know traction is an issue but God I LOVE QUICK SPOOL, Nobody try 67's or 71's on big a/r turbine ???

I'll post a picture of the current turbo braket the car came with.

Thanks a lot for all your help I really appreciate it!!!!
 
#12 ·
I ran 76's on my gts. Low end spool wasn't a problem. I ran .96 hot sides. Precision 7675s. I didnt have billet main caps so I didnt go much past 1000 rwhp. That was at 12 -13 psi. That's just barely in the efficiency map of the turbos. 16 psi would definitely get you your numbers. I went with the larger turbo because i wanted them to make the least amount of heat. I road course raced the car for 6 years. The spool characteristics and low inlet temps worked great for my use. Big ass air to water helped too along with E85.

My friend ran twin 62s on his gts and the spool was wicked fast and car was hard to control but fun as hell. Depends on what you want. A number? Or fun?

I'd keep what you have and turn the boost up a bit more and call it a day.

Sent from my LG-H932 using Tapatalk
 
  • Like
Reactions: Torquemonster
#13 ·
You could possibly have those Borg Warners rebuilt with upgraded turbines and/or compressors. I like the robustness of BW turbos, and there are a variety of different compressors and turbines offered.

Give my buddy a call or email at Work Turbochargers - High Performance Turbocharger Specialists. His name is Reed and tell him Matt sent you. ;)
 
#16 ·
GT5533R. 94mm with a tiny .81 A/R. Should come on nice and progressive with LOTS of room to grow if you want it. The power you are looking for hits right onto the sweet spot when estimating the Lb/hr with only 1.5 P/R (13-14psi). Something unusual but could work good.


I stumbled onto this turbo when looking for a big power pump gas turbo. I wanted something that didn’t hit too hard but could come on progressively. Something that would work like a HUGE Paxton. I love the way the power comes on with the Paxton but want more power than I can get out of a Novi2000 or 2500
 
#17 ·
Just trying to learn something here - how do you determine whether a turbo will boost progressively, as opposed to coming in fast? Is it because some of the bigger turbos can boost early (but modestly compared to smaller ones) then ramp up with rpms?

I like the idea of larger turbos that will still boost down low - 5psi on a big set of twins down low could be all the tires can handle anyway, then you have the top end only the big boys can deliver as boost ramps??
 
#20 ·
Low mounts are hot too with such poor hood ventilation. Id certainly want turbine covers on those tho. Probably melt the damn hood! Bright side is gravity drain !

Sent from my LG-H932 using Tapatalk
 
#23 ·
I have 6266s with built motor and ported heads. The spool really kicks in at about 3000rpm. I made 1015 rwhp at 11psi and 1027 TQ. I have had it as high as 15psi, but not on the dyno yet. I would guess I am 1100+ @ 15psi. The tire spin is a challenge, but with a good standalone EMS, you can tune it to be more well mannered. The Toyo R888s definitely helped. I am at 3psi in 1st, 6psi in 2nd, 12psi in 3rd and 15psi in 4th+, but I also ramp up the duty cycle in the higher gears so the boost builds as rpm climbs, otherwise it will shoot to 15psi by 3500-3800 and be too much. I would say 67s would have been a good turbo for 1200, but I have not ridden in a larger turbo viper so my experience is limited.
 
#24 ·
Part of the problem you are gonna run into in there cars is that with bigger turbos you won't hit full boost until very high RPMs. With my turbos I am at full boost at 4200 RPMs and I redline at 6.5 or so. Doesn't give you a lot of room to play.

On my Lambo I have full boost around 4000 RPM but I can go to 9K.

It is strange. on the lambo I cruise at 70 at 3K and on the Viper is about 1300 RPM.

A little smaller but quicker spooling turbos might be a better street application.
 
#27 ·
I'm running Comp oil less 6767's on a built Gen 1 motor. Makes over 1100whp on pump gas. They would easily eclipse 1200rwhp with good fuel. I had 7879s before, too laggy for street driving. I would NEVER run bigger turbos than the 67s unless I wanted more than 13-1400whp... Personal preference I guess.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top