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Old 04-04-2012, 10:38 PM   #21
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the super-first with bypass seems like the way to go

but instead of a bypass, a simple one-way valve would be cool. some sort of lightly sprung piston that the turbo has to suck through, but the super wont push air back through.

honestly the belt driven turbo with "freewheel" is a smarter option.
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Old 04-05-2012, 12:21 AM   #22
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Quote:
Originally Posted by y8s View Post
the super-first with bypass seems like the way to go

but instead of a bypass, a simple one-way valve would be cool. some sort of lightly sprung piston that the turbo has to suck through...
I don't think that any restriction to the turbo compressor would be a good idea.
Ak Miller usede to make such an animal, but I don't think it's the optimal solution...
(On Edit; I think that may have been a blow-through app. Oops!)

As an aside:
I do question the idea that one would want a sub 2500 full-spool. Drive-line parts stress, cylinder pressure, and internal engine stress come to mind...
I don't mind a 3k spool.
My Mark VIII has taught me a lot about powerband. Below the three-k point she's docile. Good driveability, decent mileage. Above, she wakes up. Fun.

Last edited by RattleTrap; 04-05-2012 at 03:58 AM.
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Old 04-05-2012, 04:53 AM   #23
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Quote:
Originally Posted by RattleTrap View Post
I do question the idea that one would want a sub 2500 full-spool. Drive-line parts stress, cylinder pressure, and internal engine stress come to mind...
I don't mind a 3k spool.
How is increased load on the drivetrain at -2500 going to be any different than the same load at high rpm people are already running?

You could get an m90 off a 1991 thunderbird in a junk yard. The 944 crowd has pulled those and rebuilt them for less than $300. Its better to underwork a large supercharger than over work a smaller one for intake temps and power draw on the crank.
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Old 04-05-2012, 05:07 AM   #24
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Torque.

the same load at lower RPM means that a higher amount of torque was used to achieve it, which means MASSIVe stresses on the piston crowns, rods and crank. But mostly it means bent rods.

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Old 04-05-2012, 05:41 AM   #25
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What type of supercharger are you planning on using?
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Old 04-05-2012, 12:33 PM   #26
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Quote:
Originally Posted by nitrodann View Post
Torque.

the same load at lower RPM means that a higher amount of torque was used to achieve it, which means MASSIVe stresses on the piston crowns, rods and crank. But mostly it means bent rods.

Dann
?? AFAICT stress on rods is a function of peak cylinder pressure. And torque is a function of that. RPM doesn't figure in the equation.
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Old 04-05-2012, 12:43 PM   #27
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Making the same horsepower at lower RPM is only possible by producing more torque. You know that.

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Old 04-05-2012, 12:49 PM   #28
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I have a quick spool valve in my car.
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Old 04-05-2012, 05:25 PM   #29
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Quote:
Originally Posted by JasonC SBB View Post
?? AFAICT stress on rods is a function of peak cylinder pressure. And torque is a function of that. RPM doesn't figure in the equation.
Would it not be true that, for a given VE and spark angle, peak cylinder pressure will be greater at lower RPM, as the piston will be higher up in the cylinder at the moment when complete combustion of the fuel is achieved?
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Old 04-05-2012, 06:08 PM   #30
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Dann and Joe are on it.
I should say though, my comment was a little blanket-y. If we're only talking of adding a couple of tens of Lb-Ft over stock, probably not a big deal. But if we're trying for 150+ at 2500, well... [And I should add I'm thinking more of pump-gas as opposed to E-85 or real race-gas.]
Then we need stronger, usually heavier, parts, or exotic pricey parts...
Then there's the whole cost/complexity/benefit ratio...

Hey! Here's an article talking (in fairly plain language) about this whole pressure/crank angle/burn-rate/time bit. It's not the authoritative works, but a nice primer, if oversimplified a bit.
Combustion dynamics... It's a PDF so...
Here's one on time/torque/inertia.
Most of this is probably covered in our own 'detonation' thread.

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Old 04-05-2012, 06:24 PM   #31
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It also takes time for fuel to burn and flamefront to move.
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Old 04-08-2012, 05:00 AM   #32
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Hydrodynamic lubrication is not as good at low revs.
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Old 04-09-2012, 04:59 PM   #33
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All that sounds good if your going with a V8 pushing 1200hp. But if your only going 400 or less hp. Just go T3/T4.

Superchargers usually have to get to a high rpm (sometimes mid) to get the boost you want. Turbos can kick in sooner.......

I like superchargers for track. turbos for drag.......

I just think for 400hp or less, money would be wasted.

At that point you would have a built motor any way. Run the boost high.

And if your running stock motor,,,, way too much over kill.

Good for Mustangs, but miata's,,,, probably just not going to push the gap between power adders that far......
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Old 04-09-2012, 05:12 PM   #34
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My T3/T4 spooled under 3000.

And all the hype about getting boost faster is over rated. These cars never had power before 4400 anyway. When you dump that clutch.....Its instantly useless in first and second anyway.........

Some lag is a little better in these cars for take off.....Atleast you move out of spot.

As far as wanting to use a m45 to help you on take off.. bad decision...period.
It is fun. But not the awesome spool your wanting. And you would be tightening belts like no other maxing it out.

If running stock engine. The 2560 pushes more power than you should, and spooles like a mad man.

I just cant see the efficency in turbo plus SC.

But you never know....Prove otherwise...
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Old 04-09-2012, 05:16 PM   #35
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Turbo Tim once built a twin turbo for a miata. We where all about it. But the comparison between twin and single turbo wasn't awsome like we expected.
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Old 04-09-2012, 08:02 PM   #36
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why, for manageable tq output, thats why.
The sooner your wheels start spinning from throttle the more mangable the car will be.
A turbo that has to respool causes a lag issue in throttle application.

Let me know what your t3\t4 did in terms of airflow in either lb or grams from 2k to 7k, 3k to 7k, 4k to 7k.

Look at wrc cars, sure they use turbos, but they also use ALS for a reason.

Last edited by Techsalvager; 04-09-2012 at 08:14 PM.
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Old 04-09-2012, 09:47 PM   #37
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This guy built a 600+ hp Elise using a 6265/ similar turbo and dual fuel systems with E100 in one of them for detonation resistance, then filled in the shiesty mid range with some combination of the parts from one of these kits:

http://visionfunction.com/product.php?id_product=2


He claims that the final product has a magically tame powerband in the video. There is no mention of how he routed the blower and turbo relative to each other, but they do specifically say that they just bolted the kit on and went for it, so they couldn't have used any funny business, and I would guess that they are just blowing through the blower and leaving the bypass valve shut.


Turbo Magazine built something similar with a TRD blower and Majestic T76 on a 1MZ-FE (Camry V6) powered SW20 MR2 in ~02ish. They blew the turbo straight through the blower (which was the only real option with the TRD kit) and made enough power to lift the heads on the 1MZ with what they described as a very docile, linear power band with the blower on the car, and laggy misery without it. They also postulated that the boost passing through the blower actually drove the blower belt and put some power back into the crank. That bit feels a little contrived/ in the realm of massively diminishing returns, but I guess it's plausible. You certainly wouldn't want to try that with an M45, though, as it would present a really serious restriction at any sort of worthwhile power level. A ported MP62 or Whipple 1.2L would be pretty kick ***, though.




In one-day-hypothetical-fairytale-land, I'd love to do something similar with my Ubercharger kit, if I can manage to put the power down in Street Mod autocross trim. Being as how I hear that current Street Mod Miatas are having trouble putting down 300whp, I hold little hope, but it provides an interesting exercise in academia, I guess.
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Old 04-09-2012, 10:25 PM   #38
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I only said m45 as I noticed they have 1.6l kits and its on the exhaust side, I could make an adapter will some help to bolt other superchargers on, but if I can get a cheap supercharger kit I would go for it.
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Old 04-11-2012, 10:34 PM   #39
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Wow. The Lotus is sick.

Anyway, just FYI, no comment, circa Jan 2011

RE: The VW 1.4 TSI “Twincharger”
Won "International Engine of the Year" 1.0~1.4 class 4 times consecutive and again 2009:
http://www.ukipme.com/engineoftheyear/previous04.html
"Best New Engine" 2006 + "Green Engine of the Year" 2009 (categories in IEOY)

Autocar (UK):

" ...
[VW's] 1.4-litre engine, which mixes turbocharging and supercharging, is said to be too complex and expensive to produce.

Instead, VW engineers now believe that new turbocharging technology can achieve similar results at a much-reduced cost.
..."
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Old 04-14-2012, 01:33 PM   #40
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Quote:
Originally Posted by Joe Perez View Post
Would it not be true that, for a given VE and spark angle, peak cylinder pressure will be greater at lower RPM, as the piston will be higher up in the cylinder at the moment when complete combustion of the fuel is achieved?
Given spark angle at MBT, not "for a given spark angle"...

I will guess yes, a bit, despite the oft mentioned "you want spark advance such that peak cylinder pressure occurs at 12/15/18* (I forget) ATDC."
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