karll

how do you build an engine suited for more boost? i heard something about sleeving the cylinders and other stuff but it is still somewhat of a mystery. so what all can you do to rate it for more lbs? and how much boost is too much? whats a good high number to shoot for without overkill? thanks.

nissanfanatic

Well, the strongest engine in the world isn't gonna hold up to boost if it isn't tuned right. I know of a guy that semi-built(which was rated for 550whp) his KA(nissan engine) and blew three of them from improper tuning. None of them lasted for a month. Then he installed a completely stock engine that has only been proven to hold 404whp for about 7-8 pulls. He ran 13psi(the same amount that blew the other three semi built engines) for quite some time. Point being, tuning is what really matters.

Look up some info on your engine. But typically, you will install forged internals. Pistons, rods, crank. Some engines come stock with forged internals(the KA comes with forged rods and crank/cast pistons). Sleeves are generally used on aluminum blocks or honda type blocks(IDK what they're called).

Then you most importantly will need to upgrade the fuel system. If you skimp on fuel, you will blow the engine. You will also need a system to tune it with. IDK what you plan on turboing, so I can give no insight on what to use. NO matter what, a wideband O2 sensor is a very good investment.

Post back and I'll try to help some more.

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-Cory

1992 Nissan 240sx KA24DE-Turbo: The Showcar
Stock internals. Daily driven.
12.6@122mph
496whp/436wtq at 25psi

karll

it will be awhile before i start turboing anything, im just curious about it though. i want to build up a 454 (cause thats what i hae right now) and maybe slap a turbo on it. i would rebuild the whole thing with forged parts as you mentioned. i will need to add more fuel right, since im pushin in more air? you said i would blow if i didn't add more fuel? why is that? i figured it just wouldn't run right. also, what do you mean by tuning? tune the turbo? tune the fuel system? i dunno. im still really new. thanks.

nissanfanatic

Well there are actually limits as to what AFs will allow the engine to run. I believe after the 20:1s, the engine doesn't suffer any harm, it just cuts out or doesn't run as you put it. 7:1 is the rich run limit. But in between, if the engine isn't running in a certian range, it will cause engine damage. Most engines make the best power at 12.5:1 AF. A safe tune would be at 11.5:1-12:1. Anything leaner than 12.8:1 and you are taking a risk. What happens is the combustion temperature rises to unsafe levels causing pre-ignition. Pre-ignition can easily turn into detonation. Search as both of these have been discussed many, many times.

Tuning covers all aspects of the engine. FAST is the best way to put it. Fuel Air Spark Tuning. It is also a company, but the name will help you remember. Tuning covers getting the right amount of fuel into the combustion chamber to mix with a certian amount of air. Then igniting the mixture at the correct time. You can tune things such as the cam timing and such, but you get the idea.

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-Cory

1992 Nissan 240sx KA24DE-Turbo: The Showcar
Stock internals. Daily driven.
12.6@122mph
496whp/436wtq at 25psi

karll

Hmm. So putting on turbos require a lot more than just tightening a few bolts and setting my boost. Sounds like the whole ordeal is really indepth. More research would probably be the best before I actually start bolting things on. I feel like kind of an idiot cause some of the stuff you said seems really confusing, but after a little more research I think I'll be able to do something with out blowing up my engine or myself. Thanks.

Threeyearitch

VERY TRUE!! I've seen it happen so many times... guy get's his car all tuned up and everything all nice and perdy running 6 lbs of boost say. Then he thinks, "ohh, i'll just crank up the boost!" to about 10lbs. say. And all of the sudden boom, all of your tuning's off, your curent fuelmap doesn't apply anymore, and your running very very VERY lean. Before you know it, your engine overheats, ur block melts, and ur f**ked.

nissanfanatic

Yep. I've been patiently waiting for about seven months now at 5-6psi saving up to upgrade certian things. Closing in on the tuned ECU right now to match my larger MAFS and 615cc injectors. Then its 10psi time.

Threeyearitch

Sounds good. Yeah, an ECU that can read boost levels is reeeeeealy nice, cause it can automatically adjust your fuel input and keep ur A/F ratio good. 10 psi sounds like a good goal, but be carefull on stock internals. A rod through the block is the last thing you want :P .

nissanfanatic

I have a wideband, so AFs are easy to watch. I definately plan to play it safe.

Hit_N_Run-player

with a 454 you might want to consider a supercharger instead of turbo. Unless you got loads of cash for 2x everything...

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1988 conquest TSI
-Lots of mods, finally finished WOOT!!



Horsepower sells cars,
Torque wins races!

guitarXgeek

I'd also just like to add that boost does not always = more power. There is a certain point of diminishing return, especially with small-medium sized turbos, that more boost only nets you more heat and no extra airflow. Airflow is what makes power, not necessarily the intake manifold pressure, boost (although higher intake pressures usually net higher volumetric efficiency, but that's another story).

For instance, the stock turbo on DSMs (2nd generation eclipse/talon - 4g63T) is EXTREMELY small. So small, in fact, that anything above ~16psi is way out of it's effeciency range. In essence, running 19psi on that small turbo will only give you more heat since you're out of the effeciency range of the turbo. Airflow gains will be HIGHLY unlikely, and probably non-existant.

However, with motors that are running lower boost levels, this problem is very improbable since even the smallest of turbos will see airflow gains with upped boost until 15psi or so (the stock 2g DSM T-25 turbo, I.E.)

Just thought I'd throw that in there, since it's quite relevant to the subject

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95 GSX
DSMlink, "50 Trim", and track times coming VERY SOON!

karll

yea i dunno. a blower would be probably work better for my setup, but its just somethin about a turbo ya know. no plans set in stone yet. i'll let ya'll know how it goes.

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