High-lag turbo

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awptickes

awptickes

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Ok, so the boost-bug bit me again. Only this time I'm not into it for the power aspect of it, but more of increasing drivability on the highways. Read: high-lag, low boost.

Ideally, I'd like something that spools at, or around 4k, and gives a little boost. I'm looking at a T25 or a T28, maybe a T3/T4 hybrid. A/R should be around .82 for what I'm looking for, right? Or do I have that the wrong way?

I want to be able to keep my foot out of the boost during normal driving, unless I need it. Feel free to flame, I can take it.


EDIT: My engine only pulls about 140 CFM at red line, so would a 350 cfm turbo be overkill?
 
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IMO, you want the oppositte. The Matrix and Honda both ran smaller turbos and made better MPG then stock. Having the low end tq/hp is nice for climbing hills easily on the highway. Seemed to make all the difference with my MPGs. Just my .02.
 
I would stay aways from the t25 or 25 if your looking to save gas, they spool alot faster and you will be in boost alot general around 1700rpm. Me personaly I would go with a 60 trim t3/t4, I donno what motor you have but I had one on my y8 and I would start to spool arround 3700rpm and made double the power of the tiny t25
 
I've got a D14z2, with some minor upgrades. 1396cc's of pure unadulterated power.

I'm really not interested in making more power all-around. I'm already happy with the power I've got. I'm really looking for FE increase.

So, a t3/t4 .50 or .40? I really don't understand quite how the compression ratio works, I know how to figure it, and measure it, but I'm at a loss as to how it effects things.
 
here read this it will help you understand turbos and the the sizes of trim, compression ratio has nothing to do with turbos, only with motors. also the bigger the turbo the more the cfm your putting into the motor, you have to put that into consideration, because that will affect the amount of boost that your motor will safely hold.

A smaller turbo will spool faster, but will cost you more in gas and top end power. you will also be in boost alot more.

You have a very small motor, its ok though, Ive never heard of anyone turboing that motor so good luck. personally I think a t3/t4 might be to large for that motor so I would use a t3 turbo, I think it will get you the power you want in a decent rpm range and not have a shit load of lag.

anyways here's a link to that site, read up about turboing and do alot of research before you decide to do it because it can get expensive quick.

Turbo Sizing Tech Specs - Honda Tuning Magazine
 
awptickes said:
I've got a D14z2, with some minor upgrades. 1396cc's of pure unadulterated power.

I'm really not interested in making more power all-around. I'm already happy with the power I've got. I'm really looking for FE increase.

So, a t3/t4 .50 or .40? I really don't understand quite how the compression ratio works, I know how to figure it, and measure it, but I'm at a loss as to how it effects things.
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so your not wanting more power your wanting better mpg ?
 
t3t4delsol said:
here read this it will help you understand turbos and the the sizes of trim, compression ratio has nothing to do with turbos, only with motors. also the bigger the turbo the more the cfm your putting into the motor, you have to put that into consideration, because that will affect the amount of boost that your motor will safely hold.

A smaller turbo will spool faster, but will cost you more in gas and top end power. you will also be in boost alot more.
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People have turbo'd the d14, but their goals were power. I already make about 100hp/l, so I'm happy with that.

I really want something that's easy to stay out of boost in the city. Ideally, something that spools up at over 3k.

AHHVTEC said:
so your not wanting more power your wanting better mpg ?
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Correct. Better fuel economy.

I drive about 180km/day just to get to work, and about 160 of that is autobahn. We're talking 90 mph for 45 minutes, autobahn. That's the point where I'm pretty sure I can make the improvement.
 
i could be wrong but ive never heard of a turbo getting better mpg for a motor, id just swap in a vtec e motor
 
AHHVTEC said:
i could be wrong but ive never heard of a turbo getting better mpg for a motor, id just swap in a vtec e motor
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I would swap a vtec-E head, if I could find one. I can't change the displacement, which limits me pretty severely.
 
AHHVTEC said:
i could be wrong but ive never heard of a turbo getting better mpg for a motor, id just swap in a vtec e motor
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It's not about getting better fuel economy it about staying out of boost, that's the goal he wants and that in itself will save in fuel. t3t4delsol is right, the t3 turbo will suit him fine. btw the 16g turbo is arround the same size as a t3 turbo
 
Actually, a properly tuned SMALL turbo WILL net better fuel economy if you drive the car exactly as you did before. A fast spooling small turbo will boost 1-2 psi at partial throttle, effectively increasing your engine's volumetric efficiency by pushing more air into it than would be possible all motor. It uses wasted energy to do that (your exhaust), so there's really no economy penalty as long as you keep your foot out of it. You're basically getting rid of a lot of the efficiency loss from having the throttle butterfly partially open by having positive pressure going through the intake side of the engine.

On the other hand, tune it badly or stomp on it all the time and you're definitely going to get horrible fuel economy.
 
Calesta said:
Actually, a properly tuned SMALL turbo WILL net better fuel economy if you drive the car exactly as you did before. A fast spooling small turbo will boost 1-2 psi at partial throttle, effectively increasing your engine's volumetric efficiency by pushing more air into it than would be possible all motor. It uses wasted energy to do that (your exhaust), so there's really no economy penalty as long as you keep your foot out of it. You're basically getting rid of a lot of the efficiency loss from having the throttle butterfly partially open by having positive pressure going through the intake side of the engine.

On the other hand, tune it badly or stomp on it all the time and you're definitely going to get horrible fuel economy.
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^Yep I was reading an artical somewhere (cant rmember where exactly) but some guy has an turbo S2K that was making around 300 to the wheels and getting 40ishmpg from a small, low boost setup and a slightly lean (but still safe) tune.
 
Honestly I dont know if it even said, and if I could remember where I seen the article I would link it for you. But what your trying to do is something I havent heard of before.
 
efhondakid said:
Honestly I dont know if it even said, and if I could remember where I seen the article I would link it for you. But what your trying to do is something I havent heard of before.
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SAAB has done it for years. Turbo Diesel engines are effieicent because of their turbos.
 
Wow Im a retard, I dont know why I said I havent heard of it, I meant to say I have.
 
Calesta said:
Actually, a properly tuned SMALL turbo WILL net better fuel economy if you drive the car exactly as you did before. A fast spooling small turbo will boost 1-2 psi at partial throttle, effectively increasing your engine's volumetric efficiency by pushing more air into it than would be possible all motor. It uses wasted energy to do that (your exhaust), so there's really no economy penalty as long as you keep your foot out of it. You're basically getting rid of a lot of the efficiency loss from having the throttle butterfly partially open by having positive pressure going through the intake side of the engine.

On the other hand, tune it badly or stomp on it all the time and you're definitely going to get horrible fuel economy.
Click to expand...


I mentioned this above, everyone breezed right over it. Ive done it personally with 2 different cars and BOTH had better MPG's.
 
Ok, the next question is:

How small of a turbo? I'm looking at a t25 or t20.

t20 will take less time to spool than the t25, but will it surge out? I'm cross-referencing the graphs, and it looks like everything would work fine with a t20. A lot of suzuki swift people use these size turbos, and they have worked pretty well for them. My engine is a lot like a swift as far as size goes, so I'm thinking it'll work pretty well.

So, back to the big question, t25, right? I'd like that watercooled, but there isn't a watercooled t20, so that takes me up a step to the t25.

My logic flawed?
 
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