Ka-t Theory (t3/t4 vs t28)

[480sx]

The t3/t4 50ish trim .63 vs the t2871r. I have noticed that the guys with the t2871's put down better e.t's with slightly lower trap speeds than those with the t3/t4. I believe this is because of the half weighted crank that the Ka has. While most people size up turbos for their engines based on head flow ratings, there is a whole other aspect to look at when choosing a turbo for the Ka. Simply, the KA doesnt want to make power over 5000-5500 RPMs. This means, basically, that a t28 gives you a much more usable powerband than a t3.t4 at the same boost levels.

Any thoughts?

[scheffler]

I am not sure, it is something to think about. What improvments in the powerband would you gain if you put a BB t3/t4 so that you could get boost earlier in you powerband? I am sure that there would be improvments if you did this to both turbos but if you want to run higher boost and produce more cfm from your turbo. I am not to sure. I love my T3/T4.

Definatly something to look into but i think that this might have been done.I think that the t3/t4 has been researched to be a more efficient turbo.

[Charlie240sxt]

AMS and Rick spun over 7600rpm's really over 8 i think with there ka24dets soo... it can make power up there you just have to build your motor. Stock ka's can't spin vary high because the cams dont allow for power to be made up there and the rods probably wouldn't stand the pistons speeds that would come into play.

BTW i have the stock 248/248 setup and i think it pulls alittle past 6 myself

[Florida240sx]

The crower v2 cams I had felt like it pulled past redline. Made me bounce off the rev limiter when I looked over real quick to make sure boost wasn't dropping at 19psi on my t3/t4

[sunnys14]

I've put down higher trap speeds on my t28 than t3/t4's have at the same boost level (9.5 psi put me at 111mph).

[Jookmasta]

well the higher trap times still don't make a certain turbo better than the other. it's been proven over and over again that the 50 trim is THE soulmate for the KA. Now not to say that all the t28's are worthless, but via a dyno and via compressor map calculations, the 50 trim fits the bill the best.

In regards to the faster trap times, driver skill makes a huge difference so perhaps the driver prefers the power to be in a certain place in the powerband. Also each turbo will be different at a different point in their map at a certain boost level.

In the end, your wallet and manifold will determine which route to go. Obviously, most peeps will say go the t04e route but different strokes for different folks.

[WDRacing]

Just for any Noobs that may read this thread. You can't compare turbo sizes and trims via trap speeds on different cars at different tracks at different times...EVER.

To compare a turbo you use flow rates, compressor maps, motor size and several other variables not addressed in this thread at all.

To do a true comparison you'd need EGT's for both turbo's during the run, intake air temps during the run, relative humidity and outside air temp, unless you can make the runs on the same day...doubtful though.

In a nutshell, the T3/TO4E will move the same amount of air more efficiently as the T28 at ANY boost level over 4psi.

Forgetting about the compressor side for a moment. The T2 flange will become a choke point for the KA. I'm not sure where this 5000rpm band came from, I routinely took mine to 6500. At the higher rpms the T2 flanged turbo's become heat pumps and eventually you will suffer from exhaust gas reversion.

If smaller turbo's were better for drag racing, why does EVERYONE run a bigger turbo?

WD

[steve s14]

I think that with a engine with stock cams, running a maximum of 15psi, a t28 would get you faster trap speeds because of the power coming in quick and dying off toward redline.For drag racing on a stockish engine, this would work pretty well.However, for drag racing a highly built motor running high boost levels, a larger turbo with a better efficiency match would probably work much better.I don't drag race but i want to give it a try one day so due to my lack of experience it the matter, this is just an opinion of mine.

[WDRacing]

When drag racing the car is never out of it's powerband. That being 3500 to whatever usually. The T3/TO4 is already in full boost during those rpms. Which is where it makes more power then the T28...

Thats on any engine, stock or modified.

[Neejay]

Reading this thread makes me even more comfortable about keeping my T3.

You guys are always a big help with making KA-T decisions.

[C-Kwik]

Sizing a turbo to a motor is easy enough. Matching a turbo to an application can be far more complicated. While more HP is generally more desirable, the more important factor is the mean HP used in the application. While most applications for auto racing will use the upper RPM range, some types of racing use the lower and mid-range RPMs as well...usually relatively briefly. In any race, the lower to mid-range RPMs will only be used when starting out from the start line or from the pits. But in road races and top speed challenges, this low and mid area will have little effect oon the overall race except for maybe positioning. But in a drag race, much of the race can be won or lost at the start where many cars will use the low and mid RPM's through 1st gear until they get to the high RPM's. If building a dedicated drag racing car, it is important to balance the high HP that helps build the trap speed along with the ability to get into the powerband quickly.

While not a direct comparison you can easily see how much of a difference a strong launch can affect a 1/4 mile run in this article:

http://www.roadandtrack.com/as...f.pdf

The Bugatti Veyron with it's 1001 HP and AWD pulls off an amazing 2.8 second 0-60. The Hennesey Viper, despite being up 100 HP and weighing 1000 lbs less, can only muster a 4.3 second 0-60. What this translates into though is in a 1/4 mile, the Veyron is still 1.1 seconds faster the Viper has been accelerating at a faster rate once it gets hooked up, allowing it to trp about 9 mph higher. What is important to note is that the Viper out accelerates the Veyron from 100-200 mph by 5 seconds. But the Veyron's launch put it so far out ahead, it still beats the Viper to the mile mark by .1 seconds. But you can see the HP to weight advantage has allowed the Viper to reel the Veyron in. In any case, the main point here is that the mean HP at launch in a drag race can really make or break a run.

Now going back to application of turbos, it is important to assess factors such as launch in the equation as well. If I were planning to build a car with a robust drivetrain and wrinkle slicks, I'd opt for a turbo that will provide a higher mean HP rating at the high RPM area. Simply drop the clutch from a high RPM and let the tires and high HP do the work. No need for low/mid RPM's and I get a fast E.T and trap speed. But if traction or the iontegrity of the drivetrain might become a problem launching in this manner, it might actually yield a faster E.T (which is of course what actually matters in a drag race) by being able to launch faster without the need for a violent launch.

In short matching a turbo to a motor can be discussed in ideals for the motor or ideals for the application. The T3/T4s (Especially the T04E-50) are proably a better all-around choice. There are applications where a smaller turbo or even a bigger turbo might make better sense.

The half-weighted crank has little to nothing to do with the turbo choice. There are probably some gains to be seen at high RPM's from a fully-counter-weighted crank, but the bigger factor here is that the KA wasn't engineered to flow as much air at higher RPM's. Some camshaft work and perhaps some head and valve work can remedy that easily enough (at least until the ppoint when the less than ideally balanced crank really becomes a problem). But in actuality, if you start to bump up the KA's max revs significantly, the T04 compressors stop being as good a match at the new high RPM range. In which case, there are likely better turbos to match the motor's new characteristics.

[spooled240]

When drag racing the car is never out of it's powerband. That being 3500 to whatever usually. The T3/TO4 is already in full boost during those rpms. Which is where it makes more power then the T28...

Thats on any engine, stock or modified.

agreed, anything above 3,000 rpm's in my car and the turbo spools like an srt-4

since the t3/t4 is more efficient and will pass more air due the volume, you will most likely have to up the boost more for the t28 to match the t3/t4 (especially when spool time is not a factor)

just my .02, a bigger turbo like the t3/t4 is perfect for the ka because this motor already has the low-end torque but needs the high end power

[480sx]

I've put down higher trap speeds on my t28 than t3/t4's have at the same boost level (9.5 psi put me at 111mph).

Yea, you and EZ are the reasons i started wondering about this. I didnt know you had a better trap though, i only noticed better ET's.

WD - Your completely right, there are so many variables that come into play that its not really feasible to compare. However, from all the ET's iv seen the times are pretty consistent, the t2's at lower boost levels(8-12) are faster than the t3/t4 50 trim's. I really need to find some more timeslips and do some more research, but i just tossed this thread up to see how it would do because of a recent post. Also, im curious to see how a BB t3/t4 would do vs a 2871r. That would be a better comparison really.

C-Kwik - Your right about the launch's being a huge factor in drag racing. Since most of us race without slicks, your holeshots can be sloppy at best. It would seem that a holeshot with a t2 flanged turbo is better, and that might be the reason for the better ET's.

Efficiency aside, having a turbod car is all about speed and accel. Thats what makes this a relevant discussion.

Wow this thread turned out really well. I guess most of it was already common knowledge but still it should help some people out.

[WDRacing]

WD - Your completely right

Wow this thread turned out really well. I guess most of it was already common knowledge but still it should help some people out.

Duh...of course I am...lol.

In all seriousness though. EZ unhooked his wastegate when he ran at the track last time. He sometimes reminds me of a guy I'd have peel bananas for retarded monkeys

The 2871 is a great little turbo. For a street app running 10 psi or so, I may even use it myself. But I will never be happy with such a low amount of boost.

Since we're talking about drag racing, I think it's important to note that the T3/TO4E also comes in the .48 AR which is huffing along pretty well with a max boost of 20psi. You have little to no lag and retain the efficiency of a great compressor when matched with a 50 trim wheel.

With 20psi you should be close if not passing 400whp. Match that with a good set of drag radials and a Lincoln Locker, I guarantee hours of pure fun.

WD

[480sx]

EZ man, where you at? This thread has your name all over it.

You were pretty nuts for doin that, lol nice work.

[eazye2000]

EZ man, where you at? This thread has your name all over it.You were pretty nuts for doin that, lol nice work.

I'm here, don't you worry!

Damn right I unhooked my wastegate.

I actually have a 'T' in the wastegate line that I bleed air off with. I just opened it all the way and let all the air bleed out. I'm sure some was still hitting the wastegate, but still had the desired effect (more boost)

I love my T28. It's awesome on the street. Spools like a mother'.. It's like driving a V-8. It's all power throughout the power band. No flash spool. I'm not a big fan of it myself anyways. Although I did build the motor to hold 500hp.. So maybe a turbo swap is in the future.

EZ... He sometimes reminds me of a guy I'd have peel bananas for retarded monkeys WD

F.. U..

[Florida240sx]

I love my T28. It's awesome on the street. Spools like a mother'.. It's like driving a V-8. It's all power throughout the power band.

F.. U..

If you had a t3/t4 car would feel like a v12....

[spooled240]

I love the flash spool, that's when I start catching up on the track but usually break traction on wet surfaces

When I'm launching with my car, 1st gear is really low with the 4:10 diff gear and the 15's that I usually start chirping the rear tires. Then after that I'm already in the spooling range of the rpm's so there's really never a time that my turbo is lagging through the rest of the gears...

I actually have a 'T' in the wastegate line that I bleed air off with. I just opened it all the way and let all the air bleed out. I'm sure some was still hitting the wastegate, but still had the desired effect (more boost)

redneck mbc ? lol wasn't the spool a lot slower tho?

[sickzofive]

just get a bus turbo and call it a day..

[DrifterXRPS13]

Some good suggestions WD, i might have to up mine to 20psi after i get it built and then some drag radials and well i don't know about the locker but some sort of lsd and i'll let you know how much fun it is

[Ken Park]

Ive heard some people say that the T2 turbos are too small for the KA, and I think they mean too small as in turbine inlet size. I love my GT28R! I run mine with a bottom mount manifold and have an external WG with a 9 psi spring. Its all I need for the street and to get back and forth from work.

[PantherRacer]

I just got a .50 trim T3/T4 today for my KA. I wanna see what this badboy can do!