I am ready to begin final assembly of my KA-T rebuild motor. I have several different cam setups I can go with. I have a set of 91 cams and a set of 95 cams. I am trying to figure out what combination will be best for my perticular turbo.
I am running a Z31 T3 with a .63 ar turbine housing so the turbo should spool well and still allow for decent flow in the higher RPMs. I am also using a log style manifold that may be a little restrictive at higher RPMs.
I dont cair much about low end power since the KA-T wont really be used for around town driving. My concern is that the turbo is a little small and may not be able to keep up tward redline. Should I think about setting up the cams for more mid range power?
What do you guys think I should run, 248/240, 248/232, 240/248?
Help me with my KA-T cam choice.
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SingleCamSam
- Posts: 498
- Joined: Sun May 11, 2003 4:37 pm
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SingleCamSam
- Posts: 498
- Joined: Sun May 11, 2003 4:37 pm
Yup, every day. I'll give you a more detailed description if you want to email me: [email protected] but basically it's based on a log manifold, a 14B, hacked S13 MAF, and 370cc injectors. The car holds 10psi easily to redline. I haven't had a chance to dyno or take the car to the track, but it is FAST. I spanked a new 350Z the other day, should have seen the look on the geeezer's face! I'd say the car's making about 220 or so whp and judging from the race with the Z i'd put it at about 13.7 or so on street tires.
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Redline240
- Posts: 892
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- Car: 95 240sx
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SingleCamSam
- Posts: 498
- Joined: Sun May 11, 2003 4:37 pm
It's the same hotwire type maf as on the S14, it just works on a different voltage curve and is constructed a little differently. I think that's what threw people off at first. I just pulled out the AFM portion with the wire and inserted it into a hole cut into the top of a 2.6" tube. On second thought i should have made the tube larger as the car seems to be running sort of rich. I don't drive it to work but i do try to run it everyday to tweak it.
In other words, hacking the S13 MAF is just like hacking the S14 MAF. I'm pretty sure you could do the same thing to the SOHC too.
In other words, hacking the S13 MAF is just like hacking the S14 MAF. I'm pretty sure you could do the same thing to the SOHC too.
aleph1 wrote:I've heard that the Z31 turbo can hold 10psi to redline....
Well my T3 sure as hell can't.
T3 Super 60 B, which I thought was of similar size to the Z31 turbo (my T3 is .48 a/r, .60 compressor)
I don't see anyone talking about cams here, but I'm pretty satisfied with my PDM Stage II cams and how they work under 9 psi of boost....I knew I'd be boosting eventually and don @ pdm said the cams were by no means to aggressive for turboing--and people here (WDRacing, etc) have concurred.
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SingleCamSam
- Posts: 498
- Joined: Sun May 11, 2003 4:37 pm
This has been a chronic problem as long as i've had the turbo, and I bought it freshly rebuilt, so i know the wastegate, etc are in perfect condition. I've tried numerous MBC setups including the joe p mbc, have reworked my entire exhaust to free up flow, etc, and it still drops to 7.5 psi by 6000 rpm. There are NO boost leaks. I finally got fed up and ordered a T3/T04B--If that sucker doesnt hold 10 psi to redline, I think I'm going to cry.
Mark I think that the lager housing on my turbo should help allot by comparrison.
As far as for the cams, I have heard that with a turbo changing the intake cam is not as advantagous as the exaust. If this is true I should probably go with the long duration cam in the exaust side to help force the exaust through the LOG manifold.
Since Im looking for all my power up high I think I am going to try the 240/248 combo. Maybe even 248/240.
What do you guys think, most of my info is from here S13 cam link but many of these guys are running NA though.
As far as for the cams, I have heard that with a turbo changing the intake cam is not as advantagous as the exaust. If this is true I should probably go with the long duration cam in the exaust side to help force the exaust through the LOG manifold.
Since Im looking for all my power up high I think I am going to try the 240/248 combo. Maybe even 248/240.
What do you guys think, most of my info is from here S13 cam link but many of these guys are running NA though.
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sil80drifter
- Posts: 1313
- Joined: Sun Aug 18, 2002 5:53 am
- Car: 1990 240SX Hatch
hmm... just as a note... a turbo can hold as many psi as it can before blowing up, unless it's restricted somewhere down the exhaust path. So if your turbo doesn't hold boost it's something wrong with the turbo. Have you ever tried just disconnecting the wastegate hose and carefully seing how much boost you can build? This is a little dangerous but... if the wastegate is shut all the way, all the time, technically the turbo should build infinite boost... of course it won't, but you know what I mean.
My friends RX-7 never held boost until he got a good boost controlle (electronic) and then it was fine all the way to redline.
sil80
My friends RX-7 never held boost until he got a good boost controlle (electronic) and then it was fine all the way to redline.
sil80
The turbo can build quite a bit of boost (at least 14 psi), the problem is holding it at whatever boost I want (10 psi) throughout the ENTIRE rev-range.
The turbo is almost brand new, the wastegate functions perfectly, etc...I already tried using a Joe P MBC, touted as the best MBC you can get, and it did worse than the standard needle-valve setup I have right now. I'm not going to be suckered into a $250 electronic boost controller when the internals of that are nothing more sophisticated than the internals of a joe p mbc. Not to mention, plentyyyy of people use just an mbc and have no trouble boosting accurately and consistently everywhere.
I know my exhaust isn't causing restriction, at least not an appreciable amount; it's 2.5" mandrel bent turbo back, NO catalytic converter, and very straight...
I think (I'm hoping) it's simply that the turbo itself is too small, specifically the compressor, and can't boost at high rpms due to the restrictive size of the tiny compressor wheel, which is why I'm upgrading to a T04B compressor to see if it makes any difference....but right now the turbo literally cannot flow as much as I want to with its tiny compressor wheel at high rpms/boost.
I've had this dilemma for as long as i've had the car turbocharged--trust me when I say I've exhausted all possibilities in trying to diagnose what is causing the problem.
But this is quite off-topic.
My t04b comes in next week; I have a lot of other things to do to the car and hopefully by mid-april everything will be sorted out.
The turbo is almost brand new, the wastegate functions perfectly, etc...I already tried using a Joe P MBC, touted as the best MBC you can get, and it did worse than the standard needle-valve setup I have right now. I'm not going to be suckered into a $250 electronic boost controller when the internals of that are nothing more sophisticated than the internals of a joe p mbc. Not to mention, plentyyyy of people use just an mbc and have no trouble boosting accurately and consistently everywhere.
I know my exhaust isn't causing restriction, at least not an appreciable amount; it's 2.5" mandrel bent turbo back, NO catalytic converter, and very straight...
I think (I'm hoping) it's simply that the turbo itself is too small, specifically the compressor, and can't boost at high rpms due to the restrictive size of the tiny compressor wheel, which is why I'm upgrading to a T04B compressor to see if it makes any difference....but right now the turbo literally cannot flow as much as I want to with its tiny compressor wheel at high rpms/boost.
I've had this dilemma for as long as i've had the car turbocharged--trust me when I say I've exhausted all possibilities in trying to diagnose what is causing the problem.
But this is quite off-topic.
My t04b comes in next week; I have a lot of other things to do to the car and hopefully by mid-april everything will be sorted out.
Nismo makes a drop i set of 248/248 for about 380 i believe. Most dealers can order the same stuff. I checked with my local dealer--he can get them for 406.00. About the same as I would pay with shipping from http://www.nismoparts.comThese cams are great for highway runs--and great for low to midrange power and torque. You wont see a HUGE increase in top end...but it will be a nice improvement with a substantial increase non the less.
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sil80drifter
- Posts: 1313
- Joined: Sun Aug 18, 2002 5:53 am
- Car: 1990 240SX Hatch
An MBC may let the WG open, whether by accident or because it can't hold the pressure.An electronic BC will not open under any circumstances, until it senses that enough pressure has been built and only THEN the signal will be sent to open the wastegate. Building boost is unrelated to keeping it up (it only proves that the turbo can build as much as you say it did). When your boost sags at such and such rpm, it means that the wastegate opens when it shouldn't. There is no other way it will drop. No physically possible way. The only thing that will cause the boost to drop is a wastegate that opens (too early in your case). That is it. I understand you've tried a LOT of things, but as you said you haven't tried them ALL. Once you've tried an EBC, and it fails as well, THEN you can say you've tried it all. And I'll publicly eat my paper-printed replies. 
sil80
Btw, where are you measuring boost (manifold or turbo), and where are you connecting the WG actuator hose to (manifold or turbo)? If your WG actuator hose is connected to the compressor, and your boost gauge is measuring it at the manifold (or after tghe IC someplace), then there coudl be a definite difference in numbers.
sil80
Btw, where are you measuring boost (manifold or turbo), and where are you connecting the WG actuator hose to (manifold or turbo)? If your WG actuator hose is connected to the compressor, and your boost gauge is measuring it at the manifold (or after tghe IC someplace), then there coudl be a definite difference in numbers.
Okay sil80, you can buy me an EBC, and if it works, I'll refund your money 
I said myself building boost was a lot different than sustaining it...
But my turbo has NO MORE than 500 miles on it...I bought it freshly rebuilt--with a new wastegate--there's no possible way that the wastegate is malfunctioning unless its normal for these things to crap out after 500 miles of very mild use.
The WG actuator hose is connected to the only place it should be connected to, the compressor of the turbo. I never heard of connecting it to the manifold--I'm internally gated btw.
I'm measuring boost off of the INTAKE manifold, which is what counts, and which is where most people measure it off of...I don't care what boost it's at at the turbo, I need to know what exact pressure my engine is really going to see...
In any case, if I do indeed have a malfunctioning wastegate, which seems highly improbable, a T3/T04B in any case is going to be a better turbo than a T3 super 60. I'm only losing ~$50 on upgrading the turbo so if it turns out that the wastegate was the only thing that was bad, I won't be disappointed because I'll have a more efficient turbo.
We gotta stop post whoring sil80 :icesangel
I said myself building boost was a lot different than sustaining it...
But my turbo has NO MORE than 500 miles on it...I bought it freshly rebuilt--with a new wastegate--there's no possible way that the wastegate is malfunctioning unless its normal for these things to crap out after 500 miles of very mild use.
The WG actuator hose is connected to the only place it should be connected to, the compressor of the turbo. I never heard of connecting it to the manifold--I'm internally gated btw.
I'm measuring boost off of the INTAKE manifold, which is what counts, and which is where most people measure it off of...I don't care what boost it's at at the turbo, I need to know what exact pressure my engine is really going to see...
In any case, if I do indeed have a malfunctioning wastegate, which seems highly improbable, a T3/T04B in any case is going to be a better turbo than a T3 super 60. I'm only losing ~$50 on upgrading the turbo so if it turns out that the wastegate was the only thing that was bad, I won't be disappointed because I'll have a more efficient turbo.
We gotta stop post whoring sil80 :icesangel
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sil80drifter
- Posts: 1313
- Joined: Sun Aug 18, 2002 5:53 am
- Car: 1990 240SX Hatch
Oh no, I don't think your WG is malfunctioning (could be the case but I doubt it), I think that the controller is. Internal wastegates usually can't malfunction by default, because they open AGAINST the stream of exhaust, so that if something broke (like the spring) they stay shut all the time (hence kaboom).Ok so if i buy it and it doesn't work, do i get it back? this doesn't mean I'm buying it, btw, just hypothetical... oh crap, I have to apologize for jacking this thread (multiple times). Sorry, next time I'll PM the person. We'll meet again, Mark!
sil80
sil80