Which turbo for Autocross?
11-19-2008, 01:26 PM
#1
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Which turbo for Autocross? I've finally decided to ditch nitrous and go with a longer lasting power adder: turbo induction. My main concern is spool time & low rpm response. The car will occassionally see the drag strip.
My current engine mods are stock 346ci shortblock (LS1), AFR 205 (66cc) heads, 214/230 .601/.575 117 LSA cam, FAST 90/90, cometic hg, APR fasteners. The car will have a 4" turbo-back exhaust system.
My questions are:
1. What turbo offers the best compromise (top-end power vs throttle response) for autocross/auto-X events on 4.10 gears.
2. Should I change out my cam?
3. What horsepower can I expect out of 6psi on the recommended turbo?
4. Is there any hp to be had for dumping the wastegate in the atmosphere versus back into the downpipe?
My current engine mods are stock 346ci shortblock (LS1), AFR 205 (66cc) heads, 214/230 .601/.575 117 LSA cam, FAST 90/90, cometic hg, APR fasteners. The car will have a 4" turbo-back exhaust system.
My questions are:
1. What turbo offers the best compromise (top-end power vs throttle response) for autocross/auto-X events on 4.10 gears.
2. Should I change out my cam?
3. What horsepower can I expect out of 6psi on the recommended turbo?
4. Is there any hp to be had for dumping the wastegate in the atmosphere versus back into the downpipe?
11-19-2008, 02:01 PM
#2
That cam will work with such a high LSA, you're only going to run 7-8 or so psi doing autocross, and I'd go with a smaller turbo, well, as small as you can go since you'll need faster spool rather than higher psi. I think a setup like that would make somewhere around 575rwhp.
Last edited by 67Firebird455; 11-19-2008 at 06:12 PM.
11-19-2008, 05:26 PM
#5
You should be around 425-440 rwhp right now, correct?
Adding 6-8 psi from a small (properly sized) turbo should get you well into the 600 rwhp range.
Not sure about those 4.10s though....may want/need to go down to a 3.42 or so with all the torque you'll be making.
Adding 6-8 psi from a small (properly sized) turbo should get you well into the 600 rwhp range.
Not sure about those 4.10s though....may want/need to go down to a 3.42 or so with all the torque you'll be making.
11-19-2008, 07:40 PM
#6
TC70. We have a customer now running SCCA with a TC70 on a stock cube forged 6 spd car. Car is awesome.....just have to get a big enough turbine wheel to keep the EGT's down. Under sustain throttle, that is the major problem.
11-20-2008, 08:31 AM
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You should be around 425-440 rwhp right now, correct?
Adding 6-8 psi from a small (properly sized) turbo should get you well into the 600 rwhp range.
Not sure about those 4.10s though....may want/need to go down to a 3.42 or so with all the torque you'll be making.
Adding 6-8 psi from a small (properly sized) turbo should get you well into the 600 rwhp range.
Not sure about those 4.10s though....may want/need to go down to a 3.42 or so with all the torque you'll be making.
Besides the already mentioned gt67, are there other relatively small turbos that could make 600whp w/ a fast response? If going with a slightly larger turbo is more efficient, I'm assuming only the large turbos with the ceramic ball-bearing option would produce 600whp with the spool time of a small turbo. Is the ball-bearing turbos worth the extra money versus buying a smaller turbo? Would my stock shortblock be able to handle the extra CFM's of a larger BB turbo at 6-8psi?
11-20-2008, 09:01 AM
#10
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What you're talking about is boost threshold. Don't get screwed into buying a smaller turbo just because you want to lower your boost threshold because you'll be killing your motor at higher rpms. This includes restriction and huge heat buildup. Always err in the side of a bigger turbo.
Water cooled bearing journals are great. The turbo is oil lubricated, but it has water jackets around the bearing that almost prevent mineral deposits from coking up the bearing.
A change in cam would help and going back to stock would be awesome. The LSA is a killer because when the exhaust valve stays open longer it causes reversion into the combustion chamber which is a BAD thing. Honestly the stock cam is about the best thing you can do on almost any turbo build, they're so turbo friendly.
Water cooled bearing journals are great. The turbo is oil lubricated, but it has water jackets around the bearing that almost prevent mineral deposits from coking up the bearing.
A change in cam would help and going back to stock would be awesome. The LSA is a killer because when the exhaust valve stays open longer it causes reversion into the combustion chamber which is a BAD thing. Honestly the stock cam is about the best thing you can do on almost any turbo build, they're so turbo friendly.
11-20-2008, 11:25 AM
#11
EGT's under WOT climb very fast and have to be addressed when the motor never comes down off 4000-4500 and up rpms. Drag racing and runs of just WOT for short period of time is not a big problem. Scca and even worse is our road racing customers. They by far are the hardest on turbos of any of our customers.
11-20-2008, 03:56 PM
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EGT's under WOT climb very fast and have to be addressed when the motor never comes down off 4000-4500 and up rpms. Drag racing and runs of just WOT for short period of time is not a big problem. Scca and even worse is our road racing customers. They by far are the hardest on turbos of any of our customers.
11-20-2008, 04:01 PM
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11-21-2008, 07:56 AM
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I seriously wouldnt build your "turbo" setup for autoXing. I autocross and back before my turbo on about 380hp I was destroying the track N/A. on tight short autoxcourses where you only WOT for very very short periods next to no boost would be the best. I plan on running the least amount of boost possible when i autoX. Now roadracing ill be cranking it up and seeing what she can do. 
On the water cooler Topic, I just recieved my TC-78, what are the advantaged of doing water cooler? should I have went that route since ill be road racing?
On the water cooler Topic, I just recieved my TC-78, what are the advantaged of doing water cooler? should I have went that route since ill be road racing?
11-21-2008, 12:23 PM
#17
I seriously wouldnt build your "turbo" setup for autoXing. I autocross and back before my turbo on about 380hp I was destroying the track N/A. on tight short autoxcourses where you only WOT for very very short periods next to no boost would be the best. I plan on running the least amount of boost possible when i autoX. Now roadracing ill be cranking it up and seeing what she can do.
On the water cooler Topic, I just recieved my TC-78, what are the advantaged of doing water cooler? should I have went that route since ill be road racing?
On the water cooler Topic, I just recieved my TC-78, what are the advantaged of doing water cooler? should I have went that route since ill be road racing?
