less comp = more boost more wear?

[MetalHeadZaid]

would lowering compression, and increasing boost put more wear on the engine then having higher comp and lower boost? (because of the higher boost)? the reason i ask is because im planning on making about 300whp, but the problem is that i will need a bigish turbo to make any top end power, and we all know that a big turbo = lag, so my plan is to lower compression so that i can raise boost to reduce the lag. is this a good idea?

[2.2 Straight six]

i dont think that'll have too great an effect, running in and how you drive it are far more influential on wear.

[MetalHeadZaid]

good to know, thanks for the input

[UncleBob]

lag (IE, the RPM at which boost starts happening) is not improved by increasing boost. That will have no effect at all.

Lowering compression ratio will, if anything, make it more laggy with a given turbo config.

As for wear, that completely depends on the build. If its built for 300 HP, and you tune it safely, it will be good for a long time. How long depends on how much on the edge its tuned.

[beef_bourito]

Decreasing compression will make the turbocharger more laggy. also, if you're increasing boost by changing the wastgate spring or adjusting the boost controler it wont do anything for lag.

What car do you have? if you already have 200hp you wont even need that much boost to get there and you could run it very safely with very little increase in wear concidering you only really shove more air into the engine when you open the throttle a good bit.

[MetalHeadZaid]

thanks guys, i was under the impression that extra boost could spool the turbo faster but nevermind... all of this would be done to a 240sx (built ka24de, 9:1, enthalpy and safc if that info helps) my goal is 300whp, to spool between 2500 and 3000 rpm and to have as much top end as possible. from what i have learned, i think im gonna have to sacrifice spool time or top end. maybe a t3/t04e or gt2871r? i have a feeling these are too big but i know they have decent top end. suggestions would be awesome, thanks everyone.

[RandomGuy]

Originally Posted by MetalHeadZaid

thanks guys, i was under the impression that extra boost could spool the turbo faster but nevermind... all of this would be done to a 240sx (built ka24de, 9:1, enthalpy and safc if that info helps) my goal is 300whp, to spool between 2500 and 3000 rpm and to have as much top end as possible. from what i have learned, i think im gonna have to sacrifice spool time or top end. maybe a t3/t04e or gt2871r? i have a feeling these are too big but i know they have decent top end. suggestions would be awesome, thanks everyone.

The KA is not a good motor to build... and by "Built" KA24DE you mean...?

if you mean forged pistons, race rods, the works... think to yourself... WHY?
thats over $1000 gone, and the gt2871r, you are aware that it'll set you back a good bit, its a bigger disco potato type turbo... quick spooling and hard spooling.

so if you're trying to only get to 300whp
just keep the 9:1 compression, the KA block isn't as bad as it's cracked out to be... and drop a small t3/t4... use a modded SR20DET exhaust manifold, I have a friend who did that and it worked well... lets say, 8psi for example. Get the minor bolt on mods, some injectors and a decent tune and it's well past 300whp....
now if you want more than that, i wouldn't suggest a KA.

anyhow... what is your price range? and depending on that theres different routes you can go...
as a rule of thumb:
lower compression pistons will take GOBS of boost (great for high HP builds, etc)
high comp are good for NA and low boost applications. You will make more power on high compression setup on the same amount of boost pressure.

[SaabJohan]

In order to reduce lag you want to use a high compression ratio together with a low boost. The best is if you can control boost and ignition electronicly, some extra boost and less ignition advance at low speeds can improve driveablity of the engine.

If you want to reduce the lag time further, a Garrett T3 turbocharger is not the best choice. If you doesn't want to spend money on an aftermarket turbocharger, I would recommend a MHI TD04HL-18T-6 or similar (possibly a 19T and/or a 7 turbine housing). Another option is a BorgWarner K24, as found on for example Volvos R cars.

Also keep exhaust manifold volume, intake manifold and intercooler plumbing volume to a minimum. This will decrease lag time. Reduced exhaust volume also increase low speed torque (due to earlier boost).

Garrett GT2860RS or GT2871R are suitable aftermarket turbochargers.

[MetalHeadZaid]

why is the KA a bad engine to work on? there are a bunch of people who daily drive them on 300+ whp. pistons, rings, rods gaskets and bearings are to insure that everything lasts, (fuck risking stock parts, this engine will be pulling double stock hp and driven every day) and so i can choose a compression that will work best with my setup. i dont think your understanding. I DONT want any more than 300whp. i need a turbo that can provide quick spool times (2500 - 3000rpm) and i want top end. ask your friend if power falls off for him in the high rpm's. johan, do you think the gt2871r will be good for my goals?

[UncleBob]

the "disco potato" (T28/GT28) would probably fit the bill. It should spool fairly fast, and has a peak of 300ish HP, but thats about all its good for.

The question is how much boost it will take to meet your goal, and if you can acheive that on stock internals on pump gas. Thats hard to say for sure. Lowering the compression ratio would make it a definite yes. Going with forged pistons would increase the longevity of the motor also.

There is no hard simple answers in this, in generic terms. You need to find someone that is very intimate with this motor and this type of build. Only they will be able to give you the exact details you are looking for.

[Zeiss]

< Twin turbo 10:1cr at 6psi for daily driving.

[MetalHeadZaid]

haha awesome plate man, thats a badass stealth. dyno run? know what kinda numbers it puts out?

[Zeiss]

we are dynoing it next week i will let you know...personally im expecting around 270-280whp at 6psi. I think that would be a safe conservative estimate. I hope its more
It is possible to run up to 12psi...or maybe a little more
6psi is just for my daily driving

[MetalHeadZaid]

Originally Posted by Zeiss

we are dynoing it next week i will let you know...personally im expecting around 270-280whp at 6psi. I think that would be a safe conservative estimate. I hope its more
It is possible to run up to 12psi...or maybe a little more
6psi is just for my daily driving

yeah 280whp is fine, do you have the mods listed anywhere? make sure you let us know!

[Zeiss]

I will give you a sample of the list, the good stuff anyways :P
New 13G turbos
DN precat eliminators
DN performance Intercooler hard pipe upgrade
HPBC- Boost controller
Custum exhaust, no main cat.
Hybrid ECU + Datalogger cables
SAFCII + turbo timer.
Turbo XS type S BOV.
LSD Insert
K&N FIPK