looking for some answers here. I'm trying to help a buddy of mine choose a turbo so when he's ready to go boost he has the right information. Sadly, I have not gone boost yet so I only have a "basic" knowledge of boost. I know to big of a turbo can prevent you from getting to your goal (basically to much lag, your motor can't supply the spool), but how do you come to a conclusion on what turbo size is best for your goal/platform. In my case, the platforms a 420 ( no jokes haha ). While this info is to help him, it'll help me aswell. Thats why i''m asking. I know tuning is key. No way to tune means your toast for the most part. At the same time, choosing your piping/intercooler size is important as well, right? I would assume choosing to large of an intercooler/piping would also aid in turbo lag. Correct? to large of piping and to large of a core would result in alot of area to be charged before you hit boost.

A question I have is, whats the benefit of a tubular/equal length manifold over a log style? I do know that an equal length isn't really needed until a certain power range is reached and up to that point a log style would be fine. How do you know when your at that point? Any knowledge or links would be helpfull. I may be a dumbass but can't find to much on making a correct choice. Not anything I really understand anyways haha I need it broken down a little simpler before I go to "technical" with my terms and knowledge haha.

 

Motor size/ motor capabilities/compression/power goal

 

You or your friend need to read this book:

Amazon.com: Turbo: Real-World High-Performance Turbocharger Systems (S-A Design) (9781932494297): Jay K. Miller: Books

If you truly want to understand the fundamentals of turbocharging and how to properly select one.

Also search the Turbo Section for Compressor matching on 2GNT. I have a write up on how to interpret compressor maps and how to successfully map a compressor to the power requirements.

 

2.0 420a/ compression is 8:8:1 (thinking about swapping to 10:5:1 tho)/ the motor has eagle rods, pistons are .020, crane 12's (246/246), AEM adjustable gears, full crower valvetrain. So not much done to the motor, but i'm trying to land in the neighborhood of 350whp..

Just didn't know the proper way to determine your turbo size.

Dave- I'm gonna check that out now.

 

I recommend getting a 4g63 SS exhaust manifold for an Evo, have the exhaust flange cut off and replaced with a 420a flange. An Evo 8 16g would work well for that sort of power goal with excellent spool. It should be fairly affordable to have a cheap aftermarket Evo manifold/downpipe modified to fit your setup.

 

Intresting suggestion. May think about that. Every once in awhile there's a person selling 420a flanges on 2gnt. Although I was thinking about by time I go boost Dave should be able to make me one haha

from a technical side tho, what are the down sides of a turbo thats "to big" for a person's setup?

 

Too much lag, horrible powerband that is too narrow and unusable, boring car that takes too long to make boost with dull throttle response, etc... Peak power number goals are fun and all, but if you want a 350whp setup, you want to hit that 350whp as soon as possible and hold it out as long as possible. That would be a true "350whp setup". Not hitting 350 to the far right of the graph.

 

Ok, so basically what I thought. Whats the average run of an evo8 mani tho? any suggestions on brand? Although it sounds like an awesome idea running an evo8 mani/turbo on the 420a. Price is a factor aswell. I know a good log manifold for the 420 will land me between $225-$275 brand new. Turbo, depending on whether I go new or used will obviously vary between let's say $300-$550. Depending on brand/shaftplay/size/etc/etc....

 

Something of this nature would be sufficient for a very budget minded setup. A 420a flange should be cheap and having it welded on in place of the 4g63 flange won't be too costly. Spend an extra $50 to have reinforcement brackets welded to help distribute weight from the runners better and it should be a decently reliable manifold. I understand you are budget conscious with a build such as this, but if your OVERLY cheap, you will never have any sort of a reliable setup whatsoever. Expect to spend around $1200 to turbo a 420a with good knowledge of parts and what will actually work.

MITSUBISHI EVOLUTION 7-9 STAINLESS STEEL TURBO MANIFOLD | eBay

 

o, i'm not trying to be money conscience with this haha. Now if theres a way to save money i'm always open I was jusst trying to compare cost of your idea towards other ideas. i'm gonna order the book Dave suggested tho. I can always take suggestions, but until i learn in-depth myself, I wont really be able to take my car forward. Ya know.