Help me understand HP potential of S vs TT
 

I know im probably going to get my balls racked here but I am just confused.

I drive a 350Z with the Powerlab kit with a single GT3584R. It is capable of putting down 550whp. And its a single smaller turbo. And there is room for more.

I am looking at selling my car and purchasing a 370 in the near future and am excited yet I want to make sure I get the right kit on there the first time.

I inquired into the GTM stage 2 twin turbo kit. The sales rep shot me back an email stating that at 550whp I would be maxing that kit out, the GT28's with the .84.

So I am just confused as to how you can have a single turbo, that isnt all THAT much smaller than a GT28, making the same power #'s as TWO turbos of a slightly smaller size, on larger engine. Has it got all to do with the fact that they really do just drop off in efficiency at such a lower psi?

I would like for there to be room in my system for growth and I also wouldnt want to be pushing my turbo's super hard all the time.

Search feature, we just had a thread like this 2 weeks ago

Im no expert, but isn't the purpose of twin turbo is to have a smaller turbo spool quickly for low end and a bigger one for high end?

550whp is basically the accepted breaking point, so if the motor isn't built, we stay below that. The GTM TT kits have plenty of room to grow. Mr Squeeze is putting around 650whp with his. The supercharger kits from them have been shown to break 500whp and can hit the 550whp mark. So it's more of a pick your poison. Boosted performance offers a mid mount twin scroll system, S&R offer a single top mount they install (transport to them), STS offers a rear mount, and Stillen offers their SC system, but if you are looking to hit 550whp or higher, it won't get there. GTM also has a twin supercharger system available (kind of) that can push big numbers as well, but turbo's would be a cheaper option.

Lol DE, you are my daily source of entertainment

Ibtl!

Im sorry but the "sale rep" seems like he doesn't know what hes doing..

I made 500 WHP with GTM stage 1 with just 8.8PSI stock engine/transmission, Now that being said, im sure you can achieve 600 WHP mark with stage one with higher boost...

If you are going for big turbos then might as well go for Single turbo because lag is going to be there in either kit anyways...

I read that thread on Single vs TT. I am aware of benefits of setups. I am aware of the offered kits. But, his response is what threw me for a loop.

Here it is.......

"All of my statements are assuming a quality tune in which chances of detonation would be little to none. ~550rwhp is not a limitation for even 91 octane fuel on a VQ37, however it seems as though you have already made your decision. I would recommend going with turbos larger than stage 2s if you are concerned with detonation, they would be operating near there limit at around 540rwhp which drastically increases AITs. Actually we do not have cooling issues with our VQ37TTs, even being in a much warmer climate, so I could not relate to that statement."

WHen he states the stage 2 with the larger .84 ar vs .61 would be operating near their limits at 540rwhp is what concerned me. My slightly larger GT35 can hit that. See what im getting at here?

What sales rep did you talk to?

The GT2860RS turbos in our Stage 2 kit do not max out at 550whp. You can push them to 600+ no problem if you have the motor build to support the power.

I guess I should not have said rep. It was a rep for a distributor of your kits. A very well known distributor I might add.

Would you like me to PM you this information?

But yeah thats what I thought. When he told me at 540 you will be maxing them out I got confused.

OK. I didnt want to get into it but I actually just inquired about cost of a tuner kit. I told him I had ID1000's and an Aeromotive 340lph and return system and wanted to run E85. So I was wondering if they offered tuner kits. He told me they do but then told me it would be stupid to run the E if i didnt have a built engine.

A GT35 is not "slightly" larger than a GT28. It is a much larger turbo.

Well..Garrett offers 20 diffent sizes of turbos..many more different combinations, but overall sizes. There are only 2 turbos in-between the GT28 to the GT35 so i would say that it is slightly larger, for my question at hand.

Looking at the compressor maps of the two, the GT28 is around a 35 lb/min turbo. Maybe 40 if you run it all the way out to the very edge of the compressor map. At that same pressure ratio, the GT35 is moving almost 70 lb/min of air. At lower pressure ratios, they look similar, but I don't know why you would buy a GT35 and not run higher boost.

Did you ever own a Supra? Those are the only guys who I've heard use the words "small" and "GT35" in the same sentence. :icon17:

I' don't have all the technical input, but I would consider what kind of performance driving you are looking to do. This is just my 2 cents. I have had both. I've found that the Supercharger is a better option if you plan to do solo racing and/or more stoplight to stoplight (short distance). If you're doing more longer runs, a turbo might be the way to go. It's just my 2 cents. I've seen both do really well at both kinds of driving and new technologies are really helping equal the playing field.

Ok well this doesnt have to do with my initial question. But im looking for a no-lag system. I enjoy spirited street driving and stop-light to stop-light fun. But, I will take it to the track and get some 1/4's in and I am looking to get into some track use now also. But 95% of the time it will see city roads.

So for that im looking to put down between 500-540. So I guess the GT28's would be my choice if i have done my math.I would like to upgrade to the GTX's though. Possibly the BP kit. Again, the less lag for me the better.

I was use to a 350z stillen once..lol..

With turbo's, there will always be lag when coming on the throttle. Superchargers will have no delay coming on to the throttle, but when the turbo's kick in, there is no comparison to power under the curve. If I were you, I would start looking for dyno's showing when boost starts ramping up and what you find acceptable.

I actually have been doing that! I have been using excell to create graph comparisons. However it is difficult becuase some do not show boost logs.

I will tell you I am excited to see the Dyno for FI's new twin kit. From what I hear they are looking to eliminate lag all together.

For a true zero-lag setup you need a supercharger. Although, at your altitude, you may have issues with making enough boost on the off the shelf SC kits. I'm sure GTM could whip something up easily enough though. I've got the small GT28s on mine, and there's certainly lag. Not much, and well worth the trade for the additional torque, but it's still there.

I'm fairly sure there was a GTM Nismo running around here with a set of GTX28s if you really want the X. I'm kind of regretting not going with the GTX myself.

If you have a turbo/kit with zero lag, it means that you will not make power past 4000rpm, because in order to get "zero" (although there is no such thing) lag, you need a tiny turbine housing which just don’t flow enough in the mid/upper RPM’s. These engines rev to 7,500rpm, so use the RPM’s.

Superchargers…there are two kinds. There is centrifugal and roots type. With the centrifugal you will have your boost pressure (resistance to flow) increase with RPM’s. So there goes your “zero” lag out the window.


Roots type (Eaton for example) is a positive displacement pump, and builds boost instantly. However, it will only make good power in the lower RPM range, and suffer greatly up top, due to many variables that I won’t bother getting in to.

You do also realize that having a lot of power/boost in the lower RPM range is very hard on the engine/rods as well. This brings us back to the question, why do you want to have a “zero lag” setup?

A little bit of lag is almost a good thing. It gives you a second to think about whether you really meant to give it that much gas.

Lag and boost threshold aren't the same thing. Having a turbo with negligible lag doesn't equate to a turbo that runs out of breath by 4k rpm. Our Stage 1 Twin Turbo Kit is proof of that. Yes, it spools quick, and yes, it starts building boost when you so much as breathe on the gas pedal, but it still pulls all the way to redline. They aren't tiny housings, but they aren't ginormous either.

There are other positive displacement superchargers as well (Twin Screw and Eaton's new TVS) that are more efficient than the old Roots blowers, but packaging on this platform makes it difficult without extensive modification to the hood. Also, due to packaging, most positive displacement superchargers are limited to water/air intercoolers that are prone to heat soak.

Cylinder pressure is cylinder pressure and cylinder pressure directly correlates to torque. Too much of it (regardless of rpm) is a bad thing. Having a responsive turbo system that makes good mid-range torque is no worse than a laggy turbo system that makes the same amount of torque later in the rpm band. The other aspect is tuning. Tuning, tuning, tuning.

There is nothing wrong with wanting a responsive setup. Cars that run on road courses or autox really benefit from having responsive setups since the throttle is easier to modulate on corner exit...especially with rear wheel drive cars. Not everyone is a showboating street racer that wants to have the biggest horsepower numbers on the block. For some people, response is an important factor in their decision on what type of forced induction they choose.

I loved the gt35r on my old g35 set-up. It was the perfect turbo for spool time and power. I stayed stock block and put down 420/400 on a mustang dyno.
I'm not sure if the g37 would respond the same way. I highly doubt it.
U jus gotta research and decide your goals and budget.
Single or twins you'll be fine.
I'm runnin stage 2 TT kit and I'm at 540/500. My kit isn't maxed out, my motor is. So I'd say anything stage 2 and up will meet ur goals.

[QUOTE=Mike@GTM;2164021]Lag and boost threshold aren't the same thing. Having a turbo with negligible lag doesn't equate to a turbo that runs out of breath by 4k rpm. Our Stage 1 Twin Turbo Kit is proof of that. Yes, it spools quick, and yes, it starts building boost when you so much as breathe on the gas pedal, but it still pulls all the way to redline. They aren't tiny housings, but they aren't ginormous either. [/QUTE]

I am aware of that, but the OP is looking for a "no lag system". Most of the time guys refer to lag when going from say 2k rpm all the way to 7.5k. Of course the there will be lag.



Also something I already know. I used to build s/c kits using the Eaton M62 head units..(the positive displacement should have been in a bracket ^^up there)..I am well aware of the positive and negative attributes of these superchargers, as well as spatial constraints with the VQ.



Yes, I understand that. Maybe the OP needs to explain what he means by "zero lag", as it is different IMO than responsive turbo sytem. I am basing my statements on the fact that he built a twin charged VQ35, with the small Eatom M62 kit from Stillen and the PL GT35R kit. The purpose of that build, was to get boost by 2,000rpm (as I do remember reading it on the other forum). Hence me interpreting this inquiry as low RPM boost where cylinder pressure is extended over a longer period of time due to the low RPM's.

Yes. I did have the stillen and loved the POP in the throttle but of course frowned after that. Added the pl kit and it was fun. But wanted more so took off the stillen so I could have more safe power. Now looking at 370 kits I'm looking for a turbo system that has blip of the throttle response as close to a positive displacement sc as I can get.

I guess I like my power as close to on tap as possible. If there was a properly designed tvs for this id chop up my hood however badly it needed it.

Drove a vortech 350 at 400hp and wasn't impressed. Not into centrifugals.

I think the only way you might get instantaneous throttle from turbo's is to stroke it out to a 4.2L to get them spinning earlier.

But then you are stuck at the top again, where you can't flow enough exhaust throgh the turbines due to the larger displacement.

This is why it is important to ask the customer what the purpose of the build is, and the power they wish to make.

Again, I am looking for that stillen like response except for something that doesnt run out of breath right away. It will mostly be a street machine but I will take it to the strip and want to start tracking. Also, who knows, I may fall in love with tracking it and use it more often for that.

I have gotten used to the 400whp I have now. So by stepping up to an entirely new car...mostly for the fact they can hold more power, I would be looking at right around 500.

Twin charge it.

Wait..was this a smart*** comment? :rolleyes:

I'm still sleepy in the morning so I don't type as much, but twin charging will give you the low end response before the turbos kick in. Of course, this setup is a bit more complicated.

So one can setup a Stillen super charger and STS rear mount turbo setup. It was done on the 350Z.

But what about when VTEC kicks in, yo?

The reason I asked if that was a smart*** comment is because I was the one who twin-charged my 350..lol.. Well I used a PL kit instead of STS.

The guy with the STS twin charged just sold his to a guy in England. That car never made it to the states.

Oh snapz?! That's sick man. How about electric turbochargers?

http://cdn.memegenerator.net/instanc...x/27822865.jpg

This isn't exactly true. It is highly dependent on setup. Put a couple small quick spooling turbos on a z34 and tune for low end and suspect you would find a car with very little lag but perhaps more limited top end from bigger turbos. Certainly less lag than say a centrifical supercharger running 8psi pulley. Now put a higher psi pulley on your car or put a roots type supercharger on and supercharger may have an advantage to two small turbos.

On the other hand, a flatter torque curve is generally a good thing. If you're going for drivability for racing, and staying under a certain HP number for points on your dyno inspection, going for smaller turbos (or smaller SC) tuned for the low end might be your best bet. Give you a wide usable power band and don't even try to go for a tall peak out at the high RPMs.

Shamu, I'm referring to pedal delay, not boost lag. Definitely agree with what you are saying though.