Help me understand HP potential of S vs TT

SS_Firehawk

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.

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TopgunZ

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.

Chuck33079

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.

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Boosted Performance

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?

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Chuck33079

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.

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Mike@GTM

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.

elperuano

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.

Boosted Performance

[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.

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TopgunZ

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.

SS_Firehawk

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.

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Boosted Performance

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.

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TopgunZ

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.

DIGItonium

Twin charge it.

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TopgunZ

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

DIGItonium

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.

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