Is it possible to run too small of a turbo?

[jwahl16]

I was just wondering if it was possible to have too small of a turbo. LIke if your engine had significantly modded internals but lets say only a t25 or something. Besides not getting the most out of your engine, could it actually harm the engine itself?

Thanks

 

[LiquidX]

The only harm you do is try to run too much boost on the turbo pulling it out of it's efficency range and shortening it's lifespan. I wouldn't run more than 18psi on the t-25. I'd like to know why you feel concerned or rather why you are using a t25 unless that's all you have.

 

[JusMX141]

It may harm the engine by pumping it full of hot air, making it very difficult to tune knock out of the forecast. You can combat knock by using a massive intercooler (which may cause too much pressure drop on a small turbo) or by using water / meth injection.

In order to work the turbo at it's best without making too much hot air, you'd need to find that turbo's max efficiency, and then set your boost level right at that level. Say you're using a 14B, which is rated at 34 lb/min. If you're logging airflow, keep upping the boost a little at a time until you reach the max airflow the compressor can generate. Any boost beyond that is over-working the turbo, and further heating the air it's generating.

A T25 won't get you very far. These things can't even hold 18psi beyond 5k too easily, and the thrust plates literally explode if you consistently run over 15psi.

 

[romeen]

In addition to the compressor pumping in hot air as Justin mentioned the increased exhaust back pressure will also create heat in the head.

Heat-->Detonation-->Engine Damage

 

[the_mork]

Harming the turbo with too small of a turbo is one thing but harming the engine is another issue completely.

In real world practice probably not, but with Mitsubishi turbos especially you run into a problem with small hotsides causing excessive exhaust pressure which can promote knock. Low power knock is considerably less destructive to a built engine than to a stock rotating assembly but is never good. Also in weirdy neverland you could have a hotside so small that it literally choked off the exhaust flow to the point where you would have a hard time evacuating all of the exhaust gases from the engine, but then the engine would suffer more from incredibly stupid poor performance than having any actual damage.

Realistically the only thing you're going to do to a built engine with a small turbo is really hurt performance. Especially in the DSM aftermarket a built engine is just a stronger version of its former self. The engine itself doesn't have more power and significantly different characteristics just because it has forged rods and pistons, it is the airflow through the engine that makes or breaks performance (and parts). A SMIM, cams, big IC pipes, big exhaust, and cams will make the engine try to draw more air through it but it is still going to be limited by the most limiting factor which in this case is the turbo.

Turbo longevity can really be an issue though because if you have an engine that is ready to flow a lot sucking through a little straw it might be able to ingest quite a bit more air at lower boost than the turbo is designed to flow. There are two major things to consider in terms of turbo efficiency and that is pressure ratio and flow. For turbos to be at their best efficiency you have to hit points on the compressor map that fall within their efficiency curve for both. Then again the hotside will usually limit you to those areas anyways but in weirdy neverland you could put a super huge turbine housing on a tiny turbo and fall outside of its efficiency range where you'll end up with super poor performance and an overworked compressor that causes the turbo to fail prematurely.

Real life short answer is that really no you wont hurt an engine by putting too small a turbo on it.

 

[jwahl16]

ok thanks. i am planning on buying a dsm with fully built motor and it has a t3/t4 turbo which the guys shops said is too small because it cant keep up. ill just get it tuned and it should be fine. thanks for your help

 

[JusMX141]

i am planning on buying a dsm with fully built motor and it has a t3/t4 turbo which the guys shops said is too small because it cant keep up.

T3/T4 hybrids can range in size from a 46-trim compressor with a Stage 1 turbine (way too small) clear up to something like a PTE 6152, which is a GT40 compressor mated to a Stage 5 turbine, capable of generating some serious airflow.

You should find out the specifics on the turbo before you listen to some know-nothing asshat that trusts every word his shop tells him.

 

[DSMDriver69]

the t-25 is about one step above a hair dryer. even the honda guys can run it. is their actually something smaller?

 

[jwahl16]

turns out its a .50 trim. that isnt going to hurt the engine right?

 

[rEclipserGST]

turns out its a .50 trim. that isnt going to hurt the engine right?

That is not a small turbo. It can hurt the motor if you run too high of boost.

 

[fran_drivertsi]

If you run e85, you can forget about any knock: hot air, cold air, doesn't matter. E85 = no knock

 

[rEclipserGST]

If you run e85, you can forget about any knock: hot air, cold air, doesn't matter. E85 = no knock

Who told you that?

 

[jwahl16]

Yeah, i thnk i will be fine with the t3/t4 50 trim. I'll just be sure to take it easy, and get it tuned to make sure it runs with no extra stress on the engine. This would be my dd so i don't need anything breaking on me.

 

[V8killerturbo4]

If you run e85, you can forget about any knock: hot air, cold air, doesn't matter. E85 = no knock

That's not true, don't believe that. Even though E85 may be less prone to knock, it can and will happen.

 

[this_tsi_8urV8]

50 trim is fine, depending on a lot of things can flow from 350 hp to about 500whp.
Depends on what the car has. Size of FMIC, fuel and system, boost, etc.

 

[fran_drivertsi]

That's not true, don't believe that. Even though E85 may be less prone to knock, it can and will happen.

I was hoping you can read the sarcasm. Thats what the smiley face was for! In reality, e85 won't knock until the very extreme detonation conditions. For instance, if you run it VERY lean. When e85 does knock, it is usually serious detonation, that might destroy your engine.

 

[ILLiCliPSE]

That's not true, don't believe that. Even though E85 may be less prone to knock, it can and will happen.

i'll just say this, I've seen people blow motors because they saw no knock, kept turning up the boost more and more, kept advancing timing....still no knock. It'll make power...then boom. Too much power for the set up, so you gotta be careful. It's very hard to knock on E85, atleast from what I've been around.

 

[the_mork]

e85 is not a knock limited fuel. That said it isn't impossible to get e85 to knock it is just that when you do knock you are almost certainly past MBT and doing bearing damage.