if I add a t03/4 to my ka24e, wiil I need to chande the pistons, ect, or can I leave them the same miles on the motor are 75000 1990240sx

It really doesn't matter what turbo you use when it comes to your pistons, it is all how much boost you run. So if you use a t3/t4 trubo but keep the boost down then you can run it on stock pistons.

what is low psi and how much power am I looking at?

If you run 5psi=200hp if you run 7psi=230hp.

S13Ka24e wrote:It really doesn't matter what turbo you use when it comes to your pistons, it is all how much boost you run. So if you use a t3/t4 trubo but keep the boost down then you can run it on stock pistons.

Not entirely true. Different compressors have different efficiencies at different boost levels. Larger turbines also are less of a restriction as well, so they heat the exhaust valves less. The thresholds for detonation change from turbo to turbo. You also have to consider intercooler efficiency as well. Given a proper fuel system, 7-11 PSI should be a safe range for most reasonabley sized turbos for the KA.

i've been told that i can't use flat pistons, that it will cause the car to burn oil like hell, is it true or will I truly be ok....

Flat top pistons don't have any specific sealing issues that are any different than a domed or dished piston. Most high HP turbo motors use dished pistons for a lower compression ratio. Flat top pistons are more prone to detonation than are dished pistons, but assuming you get no detonation, a higher compression motor will make more power than a lower compression motor at the same given boost level.

C-Kwik wrote:Flat top pistons don't have any specific sealing issues that are any different than a domed or dished piston. Most high HP turbo motors use dished pistons for a lower compression ratio. Flat top pistons are more prone to detonation than are dished pistons, but assuming you get no detonation, a higher compression motor will make more power than a lower compression motor at the same given boost level.

True but...

COMPRESSION RATIO - Lowering the compression ratio allows the engine to run more boost with the same octane. For example, 8.0:1 vs 9.5:1 can tolerate another 3 psi. 3 psi gives 38HP. The 1.5 lower CR loses 3% (2% per point) or around 9HP in a 300HP engine. That nets 29HP (38-9=29). Now you know why OEM's use low compression ratios on supercharged engines.

AIR CHARGE TEMP - The turbo itself determines how much boost the engine will accept. Through volumetric efficiency. A larger turbine will move a greater volume of air with less heat then a smaller turbin moving the same amount of air.

BOOST - Both higher compression ratios and boost increase cylinder pressure and demand higher octane fuels to eliminate detonation. Fuel octane determines the amount of boost an engine will accept. Example: If fuel octane is 94 or you add a can of NOS Octane Booster you can typically run 8 psi.

IGNITION TIMING - Retarding ignition timing will allow the engine to run more boost but not without a penalty. 4° retard=16HP.

AIR FUEL RATIO - You can't make horsepower without fuel. Richer air fuel ratios reduce power but permit higher boost levels on a given fuel octane. Leaner ratios make more power but need lower boost so a lean mixture with high octane makes the most HP.

What causes detonation? 1. Lean fuel mixture, 2. low octane fuel, 3. excess boost, 4. lack of fuel, 5. advanced ignition timing, 6. vacuum leak, 7. "hot" spark plugs, 8. overheated engine, 9. excessive inlet temperature (underhood filter) and nemerous other things.

So yes you can keep your stock pistons, but you'll be limited to a lower psi, lets say around 8psi on high test. Purchase an alcohol injection kit and you can run 5 to 8 more psi, which will net around 40 to 100 hp depending on tune.

WD

Nebraska240sx wrote:i've been told that i can't use flat pistons, that it will cause the car to burn oil like hell, is it true or will I truly be ok....

i specifically used flat top pistons...why you say...they are able to generate more power in the cylinder..and are less prone to being a preignition source....

here is a pic of the flat tops.

Adamu which company made those for you ?

I guess with the KA there are no valve clearence problems with the pistons. I'm a believer in flat top pistons myself. Unfortunatly I usually run into valve problems.

WD

what kind of 1/4 times do you guys think i can lay down wit the T3/4 ect.?? running 15.7s@89mph now~home made CAI,guted cat,hot iignition.

Jay's 240sx put down 390hp at 25psi on a T3/T04E.

http://www.nissaninfiniticlub....shtml

s13 ka24det wrote:what kind of 1/4 times do you guys think i can lay down wit the T3/4 ect.?? running 15.7s@89mph now~home made CAI,guted cat,hot iignition.

That question is highly opinionated as you didnt give us a solid anything. Is it a T3 a T4 a t3/t40E a T3/T40B, trims, anytype of fuel enrichment, how much psi?

By that statement you could mean with one in your trunk. In that case I would say 15.8 due to the added weight hehe

Seriously if differs from setup to set up and offers nothing to base a time off of.

T3/4 turbo kit revhard manifold JE Forged Pistons crower rods Balanced and Blueprinted, Knife Edge,micropolished crank. Aluminum Flywheel, UD Underdrive Pully, ARP head bolts and Main Studs,Head /Intake maniford Ported and polished by Exturdehoning, Ferrea Valves, phaneom grip LSD KIT, Stage Four Cluch,Short Shifter KIT,JWT ecu,Fuelrail,72 lb per hr MSD Injecters,300ZXTT Fuelpump,Spearcol Intercoller,3 inch downpipe/exhaust... Im Planing on runing 20-24psi.

racing fuel/slick/

WDRacing wrote:True but...

COMPRESSION RATIO - Lowering the compression ratio allows the engine to run more boost with the same octane. For example, 8.0:1 vs 9.5:1 can tolerate another 3 psi. 3 psi gives 38HP. The 1.5 lower CR loses 3% (2% per point) or around 9HP in a 300HP engine. That nets 29HP (38-9=29). Now you know why OEM's use low compression ratios on supercharged engines.

AIR CHARGE TEMP - The turbo itself determines how much boost the engine will accept. Through volumetric efficiency. A larger turbine will move a greater volume of air with less heat then a smaller turbin moving the same amount of air.

BOOST - Both higher compression ratios and boost increase cylinder pressure and demand higher octane fuels to eliminate detonation. Fuel octane determines the amount of boost an engine will accept. Example: If fuel octane is 94 or you add a can of NOS Octane Booster you can typically run 8 psi.

IGNITION TIMING - Retarding ignition timing will allow the engine to run more boost but not without a penalty. 4° retard=16HP.

AIR FUEL RATIO - You can't make horsepower without fuel. Richer air fuel ratios reduce power but permit higher boost levels on a given fuel octane. Leaner ratios make more power but need lower boost so a lean mixture with high octane makes the most HP.

What causes detonation? 1. Lean fuel mixture, 2. low octane fuel, 3. excess boost, 4. lack of fuel, 5. advanced ignition timing, 6. vacuum leak, 7. "hot" spark plugs, 8. overheated engine, 9. excessive inlet temperature (underhood filter) and nemerous other things.

So yes you can keep your stock pistons, but you'll be limited to a lower psi, lets say around 8psi on high test. Purchase an alcohol injection kit and you can run 5 to 8 more psi, which will net around 40 to 100 hp depending on tune.

WD

Compression Ratio - I can't verify the numbers off the top of my head, but assuming all else equal, you are probably correct. But its an assumption, as you said, efficiency affects airflow.

Air Charge Temp - This is a generlization which is for the most part true, but remember that efficiency is measured with pressure ratios in mind. For a given amount of airflow, efficiency can change drastically depending on the pressure ratio(boost). I would find a statement that the peak efficiency island would be located in an area of higher airflow to be more correct, but even that statement isn't totally correct either. There are too many variables to consider.

Boost - Fuel Octane in that of itself does not determine the amount of boost. Assuming the same motor, you also have to provide enough fuel.

Air Fuel Ratio - You are correct about richer mixtures being less detonation prone. The atomization of the extra fuel(Liquid to gas) absorbs a lot of heat, much the same way that water injection does, but water absorbs more heat in the process. However, Leaner mixtures do not necessarily require you turn the boost down. You can run the same boost and lean it out to just before it starts to detonate and that would give you the most power. But mixtures have more to do with fuel for a given amount of air. So you can run a motor so that it is lean or rich at all times.

I'm not exactly trying to pick apart your post btw. You have a lot of good points. Just felt it needs to be more clear.

I agree with most of what you said, I just try to make things sound a lamen as possible. That way everyone can understand and get the basic jist of the point.

I know boost isn't completely octane dependant but they are almost hand in hand. As I'm sure you know that the higher octanes burn slower and colder giving a charge less apt to detonation.

I use alcohol injection personally, I have been for years. I've always had the excellant results. Add alcohol till the engine bogs, then add boost. That way your making sure you stay rich instead of lean while your increasing the boost. Rather then just turning it up and watching for knock the backing it off slightly.

I also agree with you on running your engine lean enough to barely escape detonation. But I've also been through 5 engines in my Skyline. But thats where the power is, you won't find any race teams running on the safe side.

BTW...feel free to pick apart any misimformation I might be posting. I, unlike alot of people, like to be corrected so as to not pass on any bad intell to the guys just starting out.

HAPPY THANKSGIVING

WD