Question for all you small turbo guys

[vadem]

I know alot of you run like t25's and small t3's. Im going to be running a t3 ar.48. What does the car act like on say 7-9 lbs of boost, my cars clutch Is prettty firm im hoping I wont have to get a perfomance cluctch soon, ive heard that t25 on ka hit hard do you think stock cluch will hold up for a few months? Oh yeah please say what turbo and when you hit full boost. Do you loose traction pretty easily in like 1-2nd gears? Anyway thanks.

[Structure240sx]

markEmark has a t3 on his. he says boost hits right away but drops off from 9psi to about 6psi around 5000rpms i think. t25 would hit a lil sooner but drop off sooner too

[j-z]

i had a straight t3 with a .48 a/r on my lude which had a displacement of 2.3l. it was also bored slightly over, not much though. but yeah it was a joke on how respnsive that thing was. i loved driving my car on the street. if i was just going normal in 2nd gear then hit it i would light them up and spin all the way till the rev limit. and there wasnt even a point in trying to start in first. your clutch will go fairly soon. i had a act hdss clutch on my car and it was a perfect match. and markemarks car drops off cause his boost controler, its not the size of his turbo. i ran 10 psi all day every day with no problems with a straight t3. i think a t25 would be way to small to even play with. try and look for a turbo from a svo musting or a turbo bird. the autos had a .48 a/r and the manuals had a .63 a/r so if you want insta spool find an auto.

[andrave]

damn dude I just posted and it didn't register any of it...**** anyway I was gonna say that .48 is probably too small to hold boost to redline on the ka...thats an awfully small turbine. Are you using internal or external wastegate? I'd be afraid of boost creep with internal, might want to check into that.But if you did stick with it I'm sure that boost would be pretty much immediate.

[vadem]

Well its a low milege saab turbo, Im thinking of bolting up the internal wastegate(block plate) and welding on a port to the mani to do a Tial 35 mm, with external dump. What I need Is quick repose for the street, big deal so what if It drops a pound or two at redline. This beast will hit harder than sammy sosa. Im gonna probibly need like 265s, in the back. Its funny how small the outlet is its like one inch. Well see Ill keep you doods on my project, this is going to be a 95 s14.

Vadem

[voddka]

I formerly had one, and that bad boy started spooling by 2200 or so and hit full boost (5 psi) around 3k. If you want quick spool, thats what that turbo will definitely do.

[MarkEmark]

I have a "small" T3, I guess you could say.

T3 super 60 B, .48 a/r turbine, .60 compressor, 51 trim wheel. I don't see why there's such a vehement propensity toward getting anything but a t3 in the KA-T world.

Correct, mine did drop off from like 9 psi to 6 psi past 5k RPM. HOWEVER, that was from a too restrictive exhaust, which I have since refabricated--I'll have it on/test it out in about a week.

What I will tell you is that with just a downpipe, my T3 boosts a full 10 psi all the way to 6k rpm. So assuming your downpipe/exhaust is free flowing enough, IMO, a T3 my size is perfect. I hate lag--and mine has almost none of it. Throttle response is instantaneous--really really nice. My brother, who has A4 1.8T with a K03 running 15 psi of boost was really impressed with how insanely responsive my engine was with that turbo--you depress the throttle even a small bit, the turbo's spooled, and its making power--down low, and up top.

I make full boost pretty low--and like I said, there's very little lag. I'm very happy with the size of my turbo--and I'll see next week whether or not my newly fabricated exhaust is big enough to prevent boost drop-off.

Yes, 1st and second gear are kinda useless in my car right now, even with sticky 225 dunlops in the rear and an LSD. If you step on it in first, it will spin all the way to redline, if you shift to second, it will spin quite a bit but then finally hook up. If you step on it in second, at about 4500 or 5000 rpm it'll lose traction and start spinning to redline. That's my main problem--traction, or lackthereof. My clutch was in pretty good condition (although it was the original one and had 94k miles on it) before I turbocharged it, but it didnt take long before it'd slip in 1st/second/third--and then finally in 4th. The clutch felt perfectly fine in every gear--except when you started getting up there in the rev range, and it just slipped like nothing. I suggest an ACT street clutch; I'm real happy with mine.

I'm definitely relocating that 35 pound battery to the trunk, and I guess I'll start running a full tank of gas instead of 1/2 for weight savings.

Anyway, hope that helped.

[C-Kwik]

T3 super 60 B, .48 a/r turbine, .60 compressor, 51 trim wheel. I don't see why there's such a vehement propensity toward getting anything but a t3 in the KA-T world.

Because larger turbos have better efficiency and are less of a restriction. Even your S60 T3 at 9 psi gets down to an efficiency of about 65% towards redline. And lower efficiencies mean the turbine has to work even harder to keep the turbo spooled at that boost. Where the compresor has the peak efficiency islan is where airflow is smoothest. Smoother airflow means both less generatedheat and less restriction. Less restriction means the turbine is easier to turn. This means that more exhaust air can be diverted through the wastegate which puts less backpressure on the motor.

That's not to say your system is bad, but only that it can be better if looked at from a perspective of power and efficiency. There are lot of factors to consider, response and cost being two other major ones, but I would discount anyone saying there is one best turbo. It varies with goals and is rather subjective due to that fact. I for one, like power. I don't care much about lag. I have driven a very laggy set-up and while it certainly was not fun laggin, it made up for it when boost kicked in. The response was fine in the power band, but the boost threshold was high. Nonetheless, the car was extremely fast. and the only time there was a problem was in first gear. Which was probably better that it lagged a bit as traction would have been a nightmare getting off the line with that much power.

[Structure240sx]

i like the idea of having instant boost with a small turbo but i belive the traction issue is more important. you get all that power but u cant use it. i can almost floor 1st without spinning at all. of course i have 255's in the back. unless i drop the clutch at like 5k i almost never have a traction problem

[MarkEmark]

But wouldn't the traction be pretty unpredictable on a laggy-turbo once you hit boost, especially in the rain? ie...car takes off slow and then all of a sudden BAM, full boost, and the wheels are spinning?

I'm pretty sure if I had 255's on the rear for 17" rims I'd rarely spin my wheels as well...

[TrunkMonkey]

But wouldn't the traction be pretty unpredictable on a laggy-turbo once you hit boost, especially in the rain? ie...car takes off slow and then all of a sudden BAM, full boost, and the wheels are spinning?

unless you go immediately to WOT, the turbo is non existent.

-demetrius

[C-Kwik]

Yeah, ultimately, your foot determines how fast the car goes. The car I am referring to is a 450 RWHP Supra with a T04R. It drove quite normally when cruising and putting around town. And sure, if you floor it, the car will accelerate as boost comes on. But it's not instantaneous. My friend referred to it more like they way you feel when jet takes off down a runway. It's not like launching a fighter off a carrier.

[Nathan]

But wouldn't the traction be pretty unpredictable on a laggy-turbo once you hit boost, especially in the rain? ie...car takes off slow and then all of a sudden BAM, full boost, and the wheels are spinning?

I'm pretty sure if I had 255's on the rear for 17" rims I'd rarely spin my wheels as well...

That's why you always stay out of boost, and dont floor it in the rain Also, 255 tires aren't really giving you more traction in any way except they are probably stickier, more performance oriented tires. You will have the same sized contact patch with a 205 width tire as a 255 width tire supposing you have the same pressure in them. The only difference will be the shape of the contact patch. Thats why compound and tread design is really more important than all out size, especially for straight line applications At least, thats how I understand things.

[andrave]

255 is substantially wider than 205 so the contact patch is larger...am I missing something there?

thing is, the wider the tires the sooner you hydroplane, so thats just going to compound your wet traction problems...

[Nathan]

[QUOTE]Originally posted by andrave "]255 is substantially wider than 205 so the contact patch is larger...am I missing something there?

Yep, you are...gas laws my friend Here, lemme link you to something: http://www.nissaninfiniticlub....+same

[Phax]

...My friend referred to it more like they way you feel when jet takes off down a runway. It's not like launching a fighter off a carrier.

That's a very good way of describing laggy turbos. My buddy has a high single turbo on his Supra too. It's kind of a trip to ride in...

5mph.. laggin10mph.. laggin15mph.. something might be happening20mph.. uh, ohhh40mph.. 80mph.. can't... lean... forward...

[MarkEmark]

That's why you always stay out of boost, and dont floor it in the rain Also, 255 tires aren't really giving you more traction in any way except they are probably stickier, more performance oriented tires. You will have the same sized contact patch with a 205 width tire as a 255 width tire supposing you have the same pressure in them. The only difference will be the shape of the contact patch. Thats why compound and tread design is really more important than all out size, especially for straight line applications At least, thats how I understand things.

Actually, I'm sure my 225's are just as performance-oriented/sticky as his 255's...they're Dunlop SP SPORT 8000's, treadware 180, traction AA, temp A.

But all of you are forgetting the most important thing--mass. My 15" wheels with 225's are SUBSTANTIALLY lighter than 17" wheels with 255's. It takes a lot more to spin heavy 17" wheels with wide, heavy tires than it does to spin lightweight 15" wheels with narrow, lighter tires.

And for me, I'd rather have power/boost all the way around and no lag--it makes the car feel decidedly more naturally-aspirated--and I hate waiting for turbo's to spool up when I step on the gas. My smaller sized turbo would be especially advantageous in tight road-courses such as autocross where you need the low-end grunt/boost to rocket yourself out of corners. And I'll be autocrossing next summer. We'll see then.

Also, you need to think about what you're going to be doing with the car--My car for me is a daily driver (in nice weather, anyway)...I don't want to have to be revving it consistently past 4k for full boost/rapid acceleration--i want the boost/throttle response down low, without having to waste gas bringing it up to redline just to make the car accelerate quickly. And mine by no means runs out of juice in the upper RPMS--it hits hard, and stays hard up until 6k rpm (hopefully--we'll see with the new exhaust).

[vadem]

Im going to be wearing 19's and 265s in the back so I think Ill have some luck with traction. I really cant wait to slap this beast on, im ordering a jgs logger tommarow.

[C-Kwik]

80mph.. can't... lean... forward...

LOL!

[C-Kwik]

And for me, I'd rather have power/boost all the way around and no lag--it makes the car feel decidedly more naturally-aspirated--and I hate waiting for turbo's to spool up when I step on the gas. My smaller sized turbo would be especially advantageous in tight road-courses such as autocross where you need the low-end grunt/boost to rocket yourself out of corners. And I'll be autocrossing next summer. We'll see then.

Also, you need to think about what you're going to be doing with the car--My car for me is a daily driver (in nice weather, anyway)...I don't want to have to be revving it consistently past 4k for full boost/rapid acceleration--i want the boost/throttle response down low, without having to waste gas bringing it up to redline just to make the car accelerate quickly. And mine by no means runs out of juice in the upper RPMS--it hits hard, and stays hard up until 6k rpm (hopefully--we'll see with the new exhaust).

You'll only be waiting if you let the RPM's drop too low. It might be better to do this then force a shortshift situation on an autocross, but on any road course this should not be a problem at all. But if response is that much of a concern, keep in mind that a T3/T4 will provide great response while using a T4 compressor will put out a better efficiency over a broader range. It's all a motter of personal preference, but I really think people overrate response too much. I used to be weary of turbo lag until I felt what it's like to drive a car with a high boost threshold. You can say, "I have seen the light."

[Structure240sx]

...It's all a motter of personal preference...

couldnt have said it better myself except for spelling matter right

[MarkEmark]

Im going to be wearing 19's and 265s in the back so I think Ill have some luck with traction. I really cant wait to slap this beast on, im ordering a jgs logger tommarow.

Holy crap--are those gonna fit with no modification/rolling the fender lips? Those are some big 'uns!

If I were to do it again, I'd have gotten a T3/T4, but I'm plenty happy with my turbo right now to the point that I'll probably never change it unless I REALLY need something to waste money on.

I think laggy cars tend to give the illusion of being faster accelerators than non-laggy cars because all of a sudden you get thrown back into your seat, whereas with a car like mine, you're already pinned there :ylsuper

Yes C-Kwik, right again. You're always right. (no sarcasm meant). But for around town, I'll keep my low down boost, thank you

[andrave]

dude, you hit the nail on the head with that one...my friend had a honda and he bought a vtec controller, and you could have the vtec kick in at the stock level or adjust it, and when you adjust it really high so the engine ran really high up on the low rpm lobes and then hit the high rpm lobes, it actually made it have a ****tier, peakier powerband with no HP gain, but all the hp came on at once when it hit vtec at the higher rpm, so it felt faster... it would break the tires loose in 2nd gear when vtec hit (prelude vtec non sh).

[C-Kwik]

Truly, if you are happy, I am happy...

And thanks Sturcyture for pointing out my spelling. My fingers have been screwing up all day.

[C-Kwik]

Holy Crap...I seriously did not mean to mutilate your name! haha

[deezlins]

so a 225 tire on a 7.5in wheel has the same amount of contact as a 265 tire on a 10in wheel?

[C-Kwik]

I didn't really pay attention to the tire comments in this thread until now. But a wider tire will have more rubber touching the ground. And tires do not have a linear increase in friction with more weight. Wider tires do generally grip better all other conditions being equal. So do larger diameter tires as the contact patch would grow front to back slightly as well.

[vadem]

quote:--------------------------------------------------------------------------------Holy crap--are those gonna fit with no modification/rolling the fender lips? Those are some big 'uns

Thats what I thought I would need to do, but I was surprised on how nice they fit, They're 38 offset all around, I think ill try to squeeze in tome 285's or 295's in next time I think there is enough room. They actually dont look as huge as you would think, they look like they were made for the car, ill post pics up soon.

Vadem

[C-Kwik]

I've test fit 18x10 wheels with 275's in the rear of my S13. It fit fine with room to spare. I've heard teh S13 has about the same amount of room, but I've never confirmed it myself. Either was, the 240's seem to have lots of room in the rear tirewell.

[dareo]

i've got 225/50/16s on all 4s and they barely fit the front but tons of room in the back width wise. I dont see a 19" wheel fitting w/o some seriously low pro tires. I like to have some sidewall on there incase something ends up getting hit heheh...