Help picking a turbo
09-22-2005, 08:52 PM
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Help picking a turbo Hey all, I'm looking to build my own turbo system, for the obvious cost reasons. For a turbo, I'd like to use one off of a turbo diesel, like powerstroke, cummins, or duramax. Has anyone got any charts on these turbos? It would be going on a standard 350 (gen1) SBC engine to give some reference for the size I'm boosting. Would like to see somewhere around 8-11 psi boost and full boost at 2500-3000 rpm. Cam will be a single pattern (243* @.050 and .517 gross lift w/ .024 hot lash) to enable driving the truck w/o the turbo until I get the system completely built (no downtime). I'll gladly give any/all info needed to figure more stuff out. Also I guess it'd be good to know if any of those turbos would work to begin with. My best guess would be to go with the Powerstroke turbo since it is a Garrett and I probably wouldn't have to change the flange if I ended up aftermarket.
09-22-2005, 09:06 PM
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Just a thought, you ask what kind of turbo to get in order to run 8-11 PSI. I dont think you should be concerned with the amount of boost you want to push, you should be concerned with the HP amount and how early you want it to spool up. A huge turbo at 5 PSI can put out more power than a small turbo at 8 PSI, its about airflow not PSI. Also what is the LSA on your cam? One with a low LSA will bleed off boost, which will affect performance on a turbo car. You want a cam with a high LSA, which will prevent lobe overlap. I dont know the specs on the turbos you mentioned, so I cant help you there. Good luck though.
09-22-2005, 09:10 PM
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Yea, I know it's all in the airflow, I thought that engine size had a lot to do with that as well. But I do see your point. I'm running a 110* lsa, which I've been told by MANY cam folks is the only middle ground in going N/A and F/I. This is a carbureted engine, so I won't have the extreme lsa you EFI guys have. 106-108 is normal for street-type cams and 112-114 for nitrous, blown, turbo.
09-22-2005, 09:22 PM
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106-108 is far from a street cam, a cam like that is lopey as **** and surges like crazy. Straight drag strip cam. Streetable cams in my opinion are from 112 and up, the higher up, the smoother the idle. A good turbo cam is around 115 and up. A 110 LSA is too much overlap to run turbo with. With that LSA the turbo will not operate properly such as spooling. Nitrous cams are also completely different from FI cams. You want a bit more exhaust duration in a N2O cam, N2O works well with any LSA.
09-22-2005, 09:34 PM
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Yea, FI cams have more LSA. I'd like to see maybe a crest over 600 hp and 600 tq. Won't spin the motor over 7000 rpm and want it to spool around 2500-3000 ish. But yea, 115 LSA on carb engines is pretty wide, since carbs rely on the air's velocity through the venturi to draw gas into the a/f mix, the more exhaust overlap, the more of a "pull" that will have on the air from above the carb. That's why the guys that run super comp and comp eliminator have around 104* lsa. I guess to relate this cam profile to EFI cams, it'd be something like... 254* @ .050 w/.575" lift and 116* lsa. That's just a guess though since I haven't delt with them much.
09-22-2005, 09:42 PM
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Originally Posted by SprayedSDime
...the more exhaust overlap, the more of a "pull" that will have on the air from above the carb....
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09-22-2005, 10:26 PM
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Originally Posted by MIGHTYMOUSE
i think it would be a lot easier on you to just pick up a 63,66 or 76 regular old t4 turbo and call it a day.. they are the range you are looking for to meet your spool and hp goals.
P.S. I saw you drove to the track to run 9s.
09-22-2005, 10:41 PM
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Alot of the diesel confiured turbos use large A/R's or severly oudated units. Many are still just holset derived which are heavy and slow spooling. For a 350 with your spool requirements, a MP T70 would do the trick and spool very quickly.
Jose
Jose
09-23-2005, 12:54 PM
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Originally Posted by JZ 97 SS 1500
Alot of the diesel confiured turbos use large A/R's or severly oudated units. Many are still just holset derived which are heavy and slow spooling. For a 350 with your spool requirements, a MP T70 would do the trick and spool very quickly.
Jose
Jose
09-23-2005, 01:05 PM
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The t3 flange unit is considerably smaller and will cause some backpressure problems as the boost pressure rises. The T4 is a better fit. You best bet is a T4 with a .96A/R. Unfortunately MP does not offer the 70 T4 with anything other then a .68 A/R. But you can purchase a larger A/R housing for a reasonable price.
Jose
Jose
09-23-2005, 05:33 PM
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Originally Posted by JZ 97 SS 1500
The t3 flange unit is considerably smaller and will cause some backpressure problems as the boost pressure rises. The T4 is a better fit. You best bet is a T4 with a .96A/R. Unfortunately MP does not offer the 70 T4 with anything other then a .68 A/R. But you can purchase a larger A/R housing for a reasonable price.
Jose
Jose
Well, I've been doing some reading on your site about air consumption of a 355 chevy engine. It looks to me like keeping inside the air consumption and within the 1.6-1.8 pressure ratio area that I'm at the very bottom of that turbo's island area. Does that mean that I'll be barely using the turbo? Am I just going to be having a setup that makes virtually zero heat to achieve my low boost? Just looking at this chart is telling me that I need to make more boost and have a higher air consumption than that engine is able to do at 1.6-1.8 P/R.
09-23-2005, 05:45 PM
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You have to remember the cosumption charts that I have built are for a standard 350, nothin exotic about it. If its a built engine the VE will rise and he engine will consume more air per min. You whole goal as far as the compressor map is keeping it mainly between the surge line and choke line , which are your outer speed lines on the right of the island. Ideally you want though to stay within the major portion of the island which is the most efficient.
Jose
Jose
09-23-2005, 06:21 PM
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Thanks a ton Jose, looks like I could keep this turbo and up the boost when I stroke it (383) to keep the air out put in line w/the consumption of the larger displacement.
About the 10.2:1 compression, would that be much of an issue if the turbo is fairly efficient? I'd probably have an ice intercooler and water injection to keep things safe, just the thought that my heat rentention w/iron heads making it like 11.2:1 comp on aluminum kind of scares me.
P.S. water-air intercooler is just a much simpler setup for S10s w/V8s because fo the lack of area behind the grille. Seems kind of a win-win though.
About the 10.2:1 compression, would that be much of an issue if the turbo is fairly efficient? I'd probably have an ice intercooler and water injection to keep things safe, just the thought that my heat rentention w/iron heads making it like 11.2:1 comp on aluminum kind of scares me.
P.S. water-air intercooler is just a much simpler setup for S10s w/V8s because fo the lack of area behind the grille. Seems kind of a win-win though.