KA-T w/stock internals?

[Full Throttle]

I have read in a magazine that was pretty much devoted to the 240SX that if you decide to turbo the KA you need to replace the pistons so that the CR is 8.5:1 from the stock 9.5:1. How necessary is this? Also, if you keep the stock CR and use less boost can you get the same hp as less CR and more boost. I'm kind of confused. Please help. Thanks

[veilside180sx]

First of all welcome to Nico

Second Search, there is tons of info about this topic already addressed, and would do you well to read a lot of it to have a better understanding of it

Third the stock pistons are fine up to about 300 rwhp for everyday driveability, after that the piston rings are usually the first to go. This is of course with relation to the stock 9.5:1 compression ratio and pistons.

[bruinbear714]

I have read in a magazine that was pretty much devoted to the 240SX that if you decide to turbo the KA you need to replace the pistons so that the CR is 8.5:1 from the stock 9.5:1. How necessary is this? Also, if you keep the stock CR and use less boost can you get the same hp as less CR and more boost. I'm kind of confused. Please help. Thanks

There are numerous people running stock internals @7-8psi, including me. It's all in the fuel & ignition tuning.

[HolyShiznit]

Welcome to the boards....

Please search this has been covered ad nauseum. I am one of those that pushed the stock bottom end to it's utmost breaking point. It can be done, but each engine is different yours might fail at 3 psi, you never know. But please search....

[SloS13]

There are numerous people running stock internals @7-8psi, including me. It's all in the fuel & ignition tuning.

14psi daily here

[sil80drifter]

psi ratings are worthless if you don't say what turbo you're running. best to say what whp, then it's easy to judge what is pushing it and what is not.

sil80

[wannawangan]

Going back to topic, it is possible to go KA-T w/ stock internals. And like bruin mentioned, most of the NICO KA-T set ups use fuel and ignition tuning (i.e. Apexi S-AFCII + Walbro fuel pump + timing retard from stock base).

I am currently piecing together my KA-T kit but you can take a look at Import Auto Performance for a decent turbo kit. Email them and mention that you are a NICO member to take advantage of the special pricing.

Good Luck and Keep on a SEARCHING!

[nissanfanatic]

Trapping 107mph on stock internals. 10.5psi from a T04B.

Orion runs 12psi, traps 110mph, and does Autox. So the stock engine can hold power well.

[:: orion ::]

^^^ true.

Stock block holds up quite well, unless you detonate (evn lightly). So make sure it's tuned well, and you'll get +300rwhp out of it, easily.

- Brian

[slip80]

tuning, tuning, tuning!I'v gone through 4 motors. all three motors were bunk though. Now I'm rebuilding my ka. Keep fuel and ignition in check and you should be alright.

[nissanfanatic]

Not much holds up to detonating. Best thing I would say to do is just get a tuned ECU.

[574-240sx]

SAFC and a wideband only works so long. I think the may I want to run is 7psi on a T3/T04B until I get somekind of standalone or chipped ecu.

[C-Kwik]

SAFC and a wideband only works so long. I think the may I want to run is 7psi on a T3/T04B until I get somekind of standalone or chipped ecu.

Why? First off a wideband doesn't actually tune the motor. It is a tuning tool that you use to make fuel adjustments. Although, I believe the AEM EMS can use a wideband to self-tune. An SAFC, AFAIK, is not that advanced. Second, if an SAFC is tuned to provide the safe A/F ratios and timing issues are resolved, then there is no reason longevity will degrade as a result.

I will have to partly agree with Sil80drifter. Boost levels can be used to generalize, but turbo size does make a difference. 300 HP on a T25 will put a lot more heat into the combustion chamber than a T04E(and probably require more boost). Not only from a charge air temp standpoint but also from a backpressure standpoint. Smaller turbines generally flow less and provide more backpressure. This means less of the burnt gasses can exit the combustion chamber on the exhaust stroke. It also means the exhaust valves run hotter which can end up promoting detonation.

This being said, I do know of a 15 psi KA that has held up for years. Last I heard from this guy, he pushed it to 17 psi. He has a motor he is building for more power but has been waiting to blow the KA he is running now. And this was the plan for at least a year. He still hasn't put in the built KA yet. He was pushing close to 350HP. I know of a 15 psi KA that was doing 350 HP at the wheels I'd guess for at leat a year. I've lost touch with him, so I don'tknow his current status, but there was absolutely no problem. IvanatSPracing tested to abot 400 RWHP before he started seeing problems with the stock internals.

Now this isn't to say to simply go out and boost 15 psi. You need to make sure it's done right. Most rumors like this come about because people who do not know what they are doing and up blowing their motors and simply say the motor can't handle it as they can't accept the blow to their pride and investigate further as to what the actual cause is.

I am curious. What 240sx devoted magazine did you get this from anyways?

[Full Throttle]

SuperStreet Magazine, November 2004 Issue says:

"The bottom end of the KA is overbuilt just like the SR's bottom end, so it'll withstand a fair amount of pressure before needing upgrades. The crank and rods can stay, but as soon as a turbocharger goes on the pistons must be swapped. The KA's stock 9.5:1-compression pistons are just too high for forced induction; swap those slugs for 8.5:1 pistons, the stock compression ratio for the SR20DET."

[Florida240sx]

Please set that magazine on fire. Many of us boosting on stock ka.Some above 15psi. I'm at 7psi right now abotu to bump it up to 10. No need for lower CP .

[Nismo_Freak]

Please set that magazine on fire.

+1

Editor should shoot himself for putting SR bottom ends in the same ballpark as shotty KA parts.

[nissanfanatic]

My GOD I hate that ISSUE!

One reason is what Nismo Freak said. lol jk

But seriously... You HAVE to replace pistons to run boost on a KA??? Yea okay... AT the time, any given time, they could log onto here, ka-t.org, freshalloy, any of the major 240sx forums and find more people than they could possibly want to that are running decent boost on stock internals. I mean, I woudl think JWT of all people would know scenes how they have tuned a lot of ECUs for stock KAs....

[HolyShiznit]

Ugh, quoting Super Street... oy vey.

I dunno what to say, he freaking quoted Super Street, I got nothing....

[Nismo_Freak]

Eh don't rack him too bad, he's just wondering whats the real scope on it.

Everyone starts somewhere, and if you wanna flame someone then I'm sure we can all dig up some of our old posts and rake you guys over the coals as well.

[574-240sx]

Why? First off a wideband doesn't actually tune the motor. It is a tuning tool that you use to make fuel adjustments. Although, I believe the AEM EMS can use a wideband to self-tune. An SAFC, AFAIK, is not that advanced. Second, if an SAFC is tuned to provide the safe A/F ratios and timing issues are resolved, then there is no reason longevity will degrade as a result.

I tuned my car with the wideband. I runs a SAFCII and I knocked back timing. I said it only get you so far. The SAFC got my car running and started. I'm looking for more boost but don't trust running a SAFC and knocking back timing. I have been daily driving my car for over a year with no broblems. I guess I will give megasquirt spark and extra a try.

[240sxHitman]

well since its beenin talked about, would changing the CR to 8.5 :1 be bad, better or just as good as the stock KA CR

[C-Kwik]

I tuned my car with the wideband. I runs a SAFCII and I knocked back timing. I said it only get you so far. The SAFC got my car running and started. I'm looking for more boost but don't trust running a SAFC and knocking back timing. I have been daily driving my car for over a year with no broblems. I guess I will give megasquirt spark and extra a try.

Going back you your original statement, I was pointing out that it didn't make sense here. The wideband is a tuning tool. But once the car is tuned, you will have no need for the wideband. And you actually stated it only works for so long. This has a very different meaning. The SAFC or any piggyback system won't be somehow degrading in performance as time goes on. If anything were to falter, it would be the fuel components itself. At least in a general sense.

[C-Kwik]

well since its beenin talked about, would changing the CR to 8.5 :1 be bad, better or just as good as the stock KA CR

Lower compression lowers fuel economy slightly and off-boost drivability. Running higher CR, even under boost is better, so long as the fuel you use doesn't detonate. So there is no simple answer. It depnds on many factors.

[C-Kwik]

SuperStreet Magazine, November 2004 Issue says:

"The bottom end of the KA is overbuilt just like the SR's bottom end, so it'll withstand a fair amount of pressure before needing upgrades. The crank and rods can stay, but as soon as a turbocharger goes on the pistons must be swapped. The KA's stock 9.5:1-compression pistons are just too high for forced induction; swap those slugs for 8.5:1 pistons, the stock compression ratio for the SR20DET."

Super Street is quite the SR biased magazine. And frankly the staff lack technical qualification to be making such a statement. While lower CR is more boost friendly, they simply leave the statement completely subjective as opposed to getting more specific in saying that there will some kind of limit on how much boost the pistons will handle. Even if they were to simply say the turbo SR will be less prone to detonation under high boost. As much as I can appreciate their focus on the 240SX, they do more harm than good as far as technical information is concerned.

[Dragon_284]

Yeah as most have stated getting info from a so called "tuner" magazine isnt always the best idea. Searching for youself or asking some of our members who have plenty of experience with KA motor would be a better bet. Also the CR of the 240sx depends on what year you have. If I remember correctly the 89 240sx which came with ka24e motor had a 9.1 compression, the 90 model with the ka24e had a 8.6 compression, anything 91 and up had the ka24de motor with the standard 8.5 compression. Im sure this is right but if im not dont worry someone will chime in and bust my balls with the quickness lol.

[Jookmasta]

yes i am also running boost with stock internals and have been doing so since march. 12 psi on a str8 T3 daily. tuning is the key to any turbo setup.

[98s14inaz]

Running stock block and 12 psi here in AZ. T04b/t3, 50# injectors, z32 mafs, jwt ecu. I have my wideband hardwired into the car so I can monitor and see if there are any problems. Seeing how at wot I am seeing high 10's - low 11's afr, I think I can run at least a bar of boost.

I will however tell you that I drive around town at 7psi. I am going for longevity and only turning up the boost when I need to embarass someone or dyno/track days. And to think I almost traded this car in for a 350Z. More hp, no car payment, better gas milage 240 > 350Z.

[rn240sx]

Quote »I have read in a magazine that was pretty much devoted to the 240SX that if you decide to turbo the KA you need to replace the pistons so that the CR is 8.5:1 from the stock 9.5:1. How necessary is this? Also, if you keep the stock CR and use less boost can you get the same hp as less CR and more boost. I'm kind of confused. Please help. Thanks[/quote]220 whp for 8 months on 93 octane240 whp for 16 months on 93 octane300 whp for 6 months on 100 octane (cause of small turbine)

ALL above on STOCK internals with zero problems.

Then one day i used 93 octane on 300 whp assuming it would be ok cause it was pig rich.. But i was wrong and popped 2 rings lands... Thats what happens when u push a .48 a/r turbine to 15 psi on stock 9.5 compression.. Turbine is way too small and pushing it far causes lots of heat... and this leads to detonation... and that leads to cracking or blowing ring lands on STOCK pistons..!!

So now the motor is under COMPLETE rebuild..!!

Stock bottom end with GOOD compression will give u 300-350 whp reliably providing that your tunning is tip top shape..!!

[Red-KAT]

I got 256whp at 12-13psi w/ 12:1 AFR. TD06-20G 8cm turbo. I have been running 10psi + for...... 21 months. I hit 12 psi every day at least 6 times. Drove it to and from work every day no issues. Except the computer lately been going nuts.

I think the stock block is fine for this type of power. The only reason I stopped at that much power is my 370cc injectors are at 100% for 13psi.

[D-UNIT]

A higher CR will give you more horsepower. When I buy forged pistons i'll get the stock 9.5 to 1 CR. Lower CRs raise your detonation threshold. But you have to throw more boost at it to make the same power , but it is safer. Take a honda for example with a 10.5 to 1 CR they make about 260+ whp at 6 to 8 psi. But just one ping on stock internals and bada bing bang boom.