dont most of you think that you are gettign too big of a turbos, i mean most of you it seems run mo more then 15 psi, and that is way too little for turbos such as the t56 and up. you get shitty ass low end you hit full boost by 5k rpm and the car is dog do drive around. woulnt it make more sence to just get somethign smaller and have a much bbetter power band where your car woudl actualyl be FASTER then the one with a bigger turbo not evenm talking about how much easier and more fun it woudl be to drive. it seems most people here dont do their homework for the type of turbos they buy. usualyl the most whp i see here that peopel post are aroudn 400 i mean a small to medium t04 can do that. whats the point of gettign these humongous turbines? do i not see something? or are u just gettign teh turbine for the bragging rights and how BIG it will look when u pop your hood aka (ricer). it seems most peopel only get here half of what teh turbine can do which is NOT a good thing you want to be in its EFFICIENCY range.

I think a lot of people do it for the name. A lot of people try to build dyno queens. It's all about the props.



To each his own, eh?

While some single turbo's are "too big" for the street, there are some that are too small to make anything much over 400rwhp on street level boost. Its a small sacrifice to give up 500-1000rpms over a small single struggling to get to 400rwhp, when you can have 425-450 easily on a bigger turbo that won't die off on top end.

if you dont die off at teh top end thenu are sacrifying a bunch of low end, its better to die off and make more power inteh midrange then never to fall off.

Depends on how big of a turbo you go with. You don't necessarily loose a ton of low end. The t62-1 I ran had awsome low end, and would make my apexi turbo look like a turd all day long. Who races at low rpms anyways? If you have midrange and topend, what else do you need?

i dont alwyas rev the crap out of my car, woulnt it be nicer to have some power at 3-4k? as to where these larger turbos are just startign to spool.

I'm not sure you have ridden or driven many rx7's with single turbo's. I had full boost at 4k rpms and making hella power from there all the way to 8k rpms. Again, its how you size the turbo to what you want. You CAN have good low end and good top end with a single turbo. It might not be that perfect stock low end, but its close enough for what you gain everywhere else.

NA rx7s are not bad if you are comparing your low end to that where its GREAT then i donno. care to show a dyno chart just for comparison. i woudl want to see how great that low end realyl is. i mean to each his own

KDR rebuit motor, rebuilt turbos, Steve Kan tuned APEXi Power FC and commander, ACT streep/strip clutch, HKS downpipe, APEXi intake, GReddy Profec B.

440 rwhp, at 17 psi on a Greddy T-78 on 93 octane pump gas.

Here is some GTU dyno I found.

Ok, twins make the same amount of power as the t-78 and GTU, but 400rpms quicker (looking at the 2500rpm line). Funny how the t-78 has the same power as the GTU when they hit the gas on the dyno. At 4k rpms the twins are about 125hp and 175tq, t-78 has 150tq and 200hp, the gtu at this point isn't worth discussing. Twins are maxed out by 6500rpms at 260hp, while the t78 is in the 420hp range. So 400rpms difference in that "low end" power on a t-78 which is considered "big" for the street.

Actually, just examining the charts a little closer. It would appear the twins only have a 300rpm advantage in spool/power over a big single turbo.

wow, at 5.5k rpm you are making more HP then you are with stock twins! nice

if that first dyno is the dyno fo teh twins , then u got some beat ass twins, unless they are running in non sequential

where is the dip, if this is non sequentila then this argument is uselss since the nonsequential is worse then a comparible single due to teh flow diffrences of the exahust manifold and other flow diffrences turbo related.

i think youre just trying to drag out an argument for the sake of arguing. The fact is, a big single doesnt sacrifice much low end for the amount of top end it produces. If you like having max power at 4000rpms then i suggest a new car. Max power in a rotary will not come in until after 6000 rpm.

That FD doesn't have crap for mods. Intake, downpipe and ECU with the boost turned up?

thats pretty much the same as my buddy put down, i think 260whp is pretty good for a downpipe, catback (with cat), intake, and PFC.

That is just a beautiful A/F tuning line



The biggest thing I see is the tuning between a lot of the guys. 15 PSI on a TO4E and a T78 are big differences. And 15 psi seems to be the number used most often by the guys in the US, Seeing a T78 at 20-25 psi on the same motor with the correct fuel and tuning would definately put the numbers up there, the point is reliability, with all the fear and cost involved for rebuilding the engine, which would you prefer, a little more cost on a turbo that can sit at these power levels all day and still be reliable, or putting a turbo on the car that can barely hit the mark on the upper end. Most guys do not do specific racing, and their cars are built as daily drivers with an occasional romp at the track or local parking lot for SCCA. But when they hit the throttle in a highway race, or the dragstrip, or even in the avoid the cones mania they will be shifting in the power band, usually at the top of the rpm range, and during the shifts I do not see them worrying about low end power in the 4000 rpm range, they are more worried about how fast can they get spooled back up to the power level they need at 6000 or higher in their shift range.

Well if it makes you feel better Karhren, i'll find another dyno sheet for stock twins.

Still searching for twins...but here is a gt35/40 with tuning issues.



"My SBC-ID wasnt holding boost weel past 15 psi so we quit doing pulls unti I can figure out the problem. We added a Wastegate spring to put it closer to where the boost controller would be controlling the wastegate but it didnt help. The boost comes on fast as you can see once the car was tuned and the curve goes up fast. Very good power all the way through the RPM range for a big single turbo. I was pleased. And am goin back for a 17 psi pull with my new motor next month"



Just look at that low end!

https://www.nopistons.com/forums/pub...1047683621.gif



What is the key to low-end torque like that?



Most dyno charts I've seen show a difference of 100 between HP and torque. That last run is crazy close to a 1:1 ratio of HP to torque.

i dotn consider gt35/40 to be that big of a turbo, i consider low end to be under3k rpm and at that point from that dyno chart i see about 80 hp which i snot lal that great, a t04e woudl have about 100 hp. which is a big diffrence, also its not all abotu hp down low its more of a tq thing and when u calculate teh tq for that given moment u will see its a big diffrence stock twins at that point mak eabout 120 hp and 200 ft lbs of tq

At 2500rpms the twins had 55hp and 110tq, the gt35/40 was the same if not higher, while the t-78 hadn't begun to collect data yet. At 3k those twins had 80hp and 140tq, the t78 had 80hp and 140tq about 300-400rpms later. Unless you are crusing below 2500rpms, which is unlikely, there is very little difference to be noticed in "low end" power, and again this is comaring a big turbo to small twins. The gt35/40 is medium sized. Perfect for the street because you'll have efficeint horsepower that isn't laggy and will produce good top end that the twins could never hit.

If you want low end, buy a V8 and drive between 750rpms and 2500rpms.

whoops

here is one of the 3 put togehter, oen is the NA that has exahsut and intake and an afc, the other is an fd with a dp and mp, stock catback and intake and m2 ecu and 9 psi, and the other is a t78 iforgot at which boost level but it wasnt much, i dont have one of a gt35/40 that i cna thro in tehre just have a pic of one.

the fd had no boost controller if it did it woudl get even more power down low.

That twin turbo FD isn't making much power for those mods. Do you have any real dyno sheets?

its stage 3 m2 ecu af is flat at 10:1 so its even under there, its m2 stage 3 ecu made for more mosd and more boost, everythin on the fd is stock except fo rthe DP, MP, and the intake, and onyl 9 psi the catback is still stock and its not even facotry its a post mineke with crush bends lol.

This is a better comparison.



"On a base map (PFC), 337 rwhp / 284 lbs torque @ .83 boost. Stock block, turbos, and stock injectors for this run. A/F was solid 11's across the board"

well that one makes even more power everywhere https://www.nopistons.com/forums/pub...IR#>/smile.png so u can see how much more low end it has.



all i am tryign to say is runnig osmethign liek a t78 at 15 psi and gettign 450 at wheels and mostly using it there is plai stupid. if u want 450 at teh wheels why not just get a turbo that is efficient at 450 at wheels and have much more low end. why loose low end when u dont ahve to. i am not sayign i want a v8, i hate the v8, but i dont see how this makes sence. just tyring to help everyone out. i think peopel see the large turbos and just want to buy them withotu realizing everythign about them.

Well all this would make sense. Think about what the t78 is rated for. Well over 600whp last time i checked. The t04r is a good turbo for 450-600 The stock turbos alone can make 350whp, and there is a huge difference in size of the 2 turbos. The t78 is for a supra or something with a torquey ass motor, but thats another story...also think about how much psi the t78 can handle vs. the t04 and think when it can get that psi.



This turbo BS is just all opion. If you want crazy top end then you get the turbo that fits that spec. If you want low end to mid then you get that turbo that can do that.

I wasn't implying that...I was just asking how that guy made so much torque down low, that's all.

kahren I had asked this same question a long time ago and I forget the solid answer, but it was along the lines of making more power at lower psi. Just enough power where no one has to mess with high psi/race gas. You can also make a big single turbo hit hard on the low end if you want, just throw on a smaller turbine a/r or trim. But then ofcourse the high end would choke. That also come back to the point of why run a compressor that is made for high psi out of its effieciencey range? -> Larger turbines flow more air easier than smaller compressor wheels. But keep in mind that there are many different style compressor wheels, for a example a T76 produces a lot of power out of its compressor range from I believe it is 15-22psi more than for example a To4S that is in its efficiency range there.

The thing about big turbo's is you can run them at low boost(11 psi~) and make good power(Vosko made 400~ with 11 psi) as a daily driver, and then turn around and up the boost to 19 psi for the track and make even more power(500+ ). If you were ONLY going to stay at a certain PSI(say 15psi) then you would stick with a turbo that performs best with that boost right? Well, if the big single flows more air at a certain PSI, why wouldn't you get it? Good example of this is the T-04R vs. T-04S. R makes a little more power at 15 psi, but can be considered "big turbo".



That whole "low end" thing is crap. If you've never driven a single turbo FD, especially one with a "big single" then you have no room to talk. I was DEAD SET on staying stock twins so I wouldn't have to wrry about lag...so I tried to setup my sequential system as best I could, and on a roll I would start pulling away for about 1000 rpms...then my opponent would pass me. When I went non-sequential, I would reach full boost at 3200 rpms...figured I'd have more midrange pull....didn't matter, still kept losing. With the 62-1, I would reach full boost between 3500 and 3800 rpms. I would ANNIHILATE all the 350~ hp FD's around here with ported motors/sequential twins/etc.... They would pull away for about 500 to 1000 rpms...and then I'd catch up/pass them by the time I got to about 6000 rpms(same gear). By the time I shifted(say 2nd gear to 3rd) and topped out in 3rd gear at 8000 rpms...I was GONE.



Rotary's don't make enough "low end power" to necessitate worrying about lag. The best anti-lag is a thing called "downshifting"

Wasn't directed at you.

Which brings up a good point. The guy who bought my car was very amazed at the low end power it had, and he had a twin turbo rx7 too. He was literally afraid to push it past 5000rpms.

Oh, well in that case, https://www.nopistons.com/forums/pub...IR#>/smile.png .



But my question still stands. https://www.nopistons.com/forums/pub...1047683561.gif