How do you know what size Turbo your engine can handle?

[AaronsSupraMKIII]

How do you know how big you can go without doing damage to your engine?
Would a turbo off something else work on anything? Say a powerstroke diesel for instance. They have a decent size Garret Turbo on them, are they trimmed for a slower RPM engine? Just curious.~Aaron

 

[bigaaron]

It's more about picking a turbo that is right for the engine it will be installed on, and the intended use of that engine. There are many factors involved. The compressor map for the turbo can tell you a lot about how it will perform on your engine.

A big turbo will spool at a higher rpm, but have the potential to make more power. A small turbo will spool at lower rpm, but it will be limited on how much horsepower it can make on the top end. Putting a huge turbo on your engine does not mean you will instantly make huge horsepower, because there are so many other modifications and upgrades needed to make that happen. Also, running a lot of boost does not always translate into a lot of horsepower. Making horsepower is about flow.

You can look at the engine as a big air pump. You can run all the pressure you want on the intake, but if it can't flow through the engine because of cylinder head and exhaust restrictions, the power will be limited. If don't have a sufficient fuel system to match the increased pressure and air flow, you could run lean under boost, and that is a major cause of engine failures. Or, if you are running too much boost and not enough octane to resist detonation, major engine failures can result.

Another thing to consider when choosing a turbo, is that a huge turbo can translate into huge lag. If you are going to drive the car on the street for the most part, having a turbo that doesn't spool until 6k rpm is not going to be as much fun as it may seem when you look at that massive turbo in your engine bay. If you hit full boost at 5k and the rev limiter is at 6200, it's going to be fairly useless. Many a Supra owner has been embarrassed by another car making far less horsepower, but spooled faster and had a wider powerband.

I experienced this first hand when I was lined up with a friend a while back. He had a <300whp 1jz with stock twins, and I had a 400whp 7m with a (kinda) big Garrett turbo. We were going about 50mph, and we both hit the gas. By the time my turbo spooled, he had already pulled about 2 car lengths on me. I couldn't catch up until the top of 4th gear. He had a wider power band and faster spool.

 

[IJ.]

Math research and experience

 

[AaronsSupraMKIII]

I got alot to learn about turbo's. I bought my car with a pretty good start on mods already done. It has 3"exhaust all the way, and 3" metal downpipe, Blitz BOV, Greddy Profec specII, and the Bigger Fuel Pump.(stock injectors) I never messed with the greddy boost controller,till I red up on it. Turns out it was turned OFF the whole time I have had the car. LOL I know, I'm a Newb. So I turned it on, and set it to a low setting. (4lb) and it made a huge difference. But when I left work, it really pushed my back to the seat. The Boost Controller defaulted to 20lbs when it came back on! Which I didnt know it would do. Then it sounded like something blew up. It was the BOV. Thats the first time it has ever vented on me, and my engine light came on. Was that fuel cut? Will that hurt your engine? I will be honest, it scared the crap outta me! he he

The bigger turbo and lag makes alot of since to me. Is that why people go for a twin turbo set up? More boost and spools at lower RPM's? I always wondered what the difference between two small and one big Turbo was.


I understand now. So I would be better off just upgrading my ct26 or alittle bigger. I would like to get 400 to 450 hp. Is that possible without changing internals?(besides MHG) Was the BOV release from not enough fuel? How much boost can someone get out of a stock and an upgraded ct26?

 

[bigaaron]

It sounds like you hit fuel cut, and it's good that you did! That's the whole purpose of fuel cut, to save your engine in an overboost situation.

Doward is a good guy to ask about the topic of turbo selection.
I couldn't explain the benefits of an aftermarket twin setup over a properly chosen single turbo. From what I have seen you can get about the same spool and power from a single turbo for a lot less money, and have a much less complicated install. Although I can't honestly say I've seen and/or driven a properly chosen aftermarket twin setup.

 

[AaronsSupraMKIII]

Doward is a good guy to ask about this topic.

I couldn't explain the benifits of an aftermarket twin setup over a properly choosen single turbo. From what I have seen you can get about the same spool and power from a single turbo for a lot less money, and have a much less complicated install.

K thanks for the info. BTW I like the name. LOL ~Aaron

 

[bigaaron]

There's a few more Aarons on this board too :biglaugh:

 

[AaronsSupraMKIII]

There's a few more Aarons on this board too :biglaugh:

I knew I liked this board for a reason. lol

Is 10lbs a safe setting for my car? Or should I put it at 6lbs to be safe. I'm sorry to ask so many questions, but its my first supra. I was a stealth/3000GT man till a month ago. I sold two stealths and bought two supras! Never had a turbo before though in any car.

 

[bigaaron]

10psi should be ok, as long as your engine is in good running condition, and all the normal maintenance items are covered.

 

[Doward]

Ok, a couple of points -

A large ball bearing single, will *generally* spool quicker than two medium sized turbos.

"Large", "medium", and "small" turbochargers are all relative to the size of the engine the turbo is being used with. What might be a "large" turbo for our 3.0L 7MGTE, would be a "small" turbo on a 572ci (9.37L) big block Chevy.

To determine the size of the turbo your engine can handle, you must compare the flow requirements of your engine and how much power you wish to make, to the turbocharger compressor's flow map.

This is why anyone that PM's me with any questions of what size turbo they should go with, gets the standard response "How much power do you want to make, and what are your goals with the vehicle?"

Yes, you most likely hit fuel cut - isn't it a great thing to have?

For 400-450rwhp, boost only, I think that will be a little outside the range of the 57 trim, for daily driving.

I'd look into one of the bigger bolt on turbos - the JT61 would probably be my specific choice for you, running around 16-18psi, on a MAFT-Pro + 550s.

11-12psi is the maximum I would run on the stock CT26 (and not just because that is right under fuel cut, either - Toyota's engineers knew exactly what they were doing there)

 

[AaronsSupraMKIII]

K thanks for the info. It's a learn as I go thing, but its fun learning. (So Far)
A blown HG or Engine wouldn't be fun.