Anyone have experience with superchargers and blow through with external wasting?

I'm mulling over the possibility of setting up an unthrottled M62 (smallest, cheapest, positive displacement super I can reliably find) blowing into an air to liquid intercooler and then to 4 throttle bodies & external wasting.

Does anyone have any experience remotely close to that? My biggest concern is setting up the external wasting properly. I'd like to peg the PSI at X. And that would be what it was regardless of engine RPM and Throttle Position. Would it be as simple as figuring out the right size of injectorless TB with the right spring to throttle the external wasting?

I understand the real question is why, but if anyone with some experience with external wasting could humor me I'd appreciate it.

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Andrew M
Onterrible
30ish

what? Why/

Can't you TRY an easy method like a correctly sized turbo, not TOOOOOOOOOOOOooooooooooooo big and not Tooooooooooooooooooo small, a waste gate and ya know easy things???


Am I just getting old or sumpinz?

Oh yeah/ Why was I NEVER into trick?

Cause simple is always better.

Simple.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

john vanlandingham Wrote:
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> what? Why/
>
> Can't you TRY an easy method like a correctly
> sized turbo, not TOOOOOOOOOOOOooooooooooooo big
> and not Tooooooooooooooooooo small, a waste gate
> and ya know easy things???
>
>
> Am I just getting old or sumpinz?
>
> Oh yeah/ Why was I NEVER into trick?
>
> Cause simple is always better.
>
> Simple.


I hear you. Hence why I said humor me

My 1200 cc motor is 8:1.. so forced induction is looking real good.

A supercharger's etc weight can be placed most beneficially (making the car more, not less balanced).. and I'm thinking it MAY be possible to ditch the crank driven fan to cool the cylinders and instead use an electric and cooled wasted boost. That and I'm not looking for crazy boost, more like consistant early boost.

A turbo is definitely the easy answer.

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Andrew M
Onterrible
30ish

Why independent throttles? It's not like there is going to be a significant difference in throttle response.

Normally you just choose a pulley size for the boost you'd like. It's positive displacement, after all. That's also why most people (except Ford, because they wanted a front mount intercooler on the 3.8) put the throttle plate upstream of the unit.

I'm sure you could change the setup on the internal bypass valve so that it opens under pressure instead of vacuum, but why? You'd just be overspinning the blower and then bypassing what's unused.

---

Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

Pete Wrote:
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> Why independent throttles? It's not like there is
> going to be a significant difference in throttle
> response.

It's not so much for throttle response, although I hear it helps (read on)

> Normally you just choose a pulley size for the
> boost you'd like. It's positive displacement,
> after all. That's also why most people (except
> Ford, because they wanted a front mount
> intercooler on the 3.8) put the throttle plate
> upstream of the unit.
>
> I'm sure you could change the setup on the
> internal bypass valve so that it opens under
> pressure instead of vacuum, but why? You'd just
> be overspinning the blower and then bypassing
> what's unused.

The blower is a M62 and I'm putting it on a 1.2l motor. It's HUGE for the engine. I picked up an M62 because it's 1/5th the price of the harder to find M45. If you use a throttle upstream of the blower, this works well for not bending throttle plates etc, but unless you have an internal bypass it's doing a lot of work sucking against the closed / half open throttle.

The engine I'm putting it on is air cooled, I'm going to air-to-liquid cool the boost regardless, and was thinking I can setup the blower to run at peak efficiency, cool the boost, figure out what I can safely use and waste the rest blowing it over the air cooled cylinders. Obviously I will have to meter the air AFTER the downstream throttles.

Blow through ITBs is a little on the ridiculous side, but the porsche guys seem to swear by them.. and they can't be wrong

Besides, having an internal bypass seems like a good way to heat everything up.

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Andrew M
Onterrible
30ish

There must be some good reasons for ITB's, especially on small engines as this is the only setup seen on crotchrockets...

---

Jay Woodward
Snohomish, WA
'90 Mazdog Frankenprotege
Chronologically, 46...

Jay Wrote:
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> There must be some good reasons for ITB's,
> especially on small engines as this is the only
> setup seen on crotchrockets...

They're balking at blow through ITBs.

My understanding is they are good for all the same reasons in a blow through setup, with the added wrinkle of fucking up a butterfly or throttle shaft from pressure. With a positive displacement blower, that could be snap off throttle at 8k rpm and over reving the engine. So you need some way to handle situations like that.

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Andrew M
Onterrible
30ish

Ah so, makes sense. yeah I guess I can't see a flow advantage to itb's when the engine is forcefed. Do the turbo Hayabusa's get rid of theirs, or do they hope for the best?

I like the idea of a blower 'steada a turbo, better potential reliability and no need for antilag. I took a real close look at Rotrex blowers, a way cool compact little selfcontained oil supply blower that I think would be just the thing for the rallycar, if I could find a sugardaddy to buy it for me... gad what was it, 4 grand?

---

Jay Woodward
Snohomish, WA
'90 Mazdog Frankenprotege
Chronologically, 46...

Jay Wrote:
-------------------------------------------------------
> Ah so, makes sense. yeah I guess I can't see a
> flow advantage to itb's when the engine is
> forcefed. Do the turbo Hayabusa's get rid of
> theirs, or do they hope for the best?
>
> I like the idea of a blower 'steada a turbo,
> better potential reliability and no need for
> antilag. I took a real close look at Rotrex
> blowers, a way cool compact little selfcontained
> oil supply blower that I think would be just the
> thing for the rallycar, if I could find a
> sugardaddy to buy it for me... gad what was it, 4
> grand?
>
> Jay Woodward
> Snohomish, WA
> '90 Mazdog Frankenprotege
> Chronologically, 40...

Yikes..the whole from Chevy was about $2600 for my kids car. 2 years later we have had ZERO trouble. Pulls from idle thru 7k, 10psi, 225hp at wheels and lost 1mpg.

Jay Wrote:
-------------------------------------------------------
> Ah so, makes sense. yeah I guess I can't see a
> flow advantage to itb's when the engine is
> forcefed. Do the turbo Hayabusa's get rid of
> theirs, or do they hope for the best?
>
> I like the idea of a blower 'steada a turbo,
> better potential reliability and no need for
> antilag. I took a real close look at Rotrex
> blowers, a way cool compact little selfcontained
> oil supply blower that I think would be just the
> thing for the rallycar, if I could find a
> sugardaddy to buy it for me... gad what was it, 4
> grand?

Seems like forcefeeding ITBs is quite common with turbos (and people argue it's better). The biggest problem with a positive displacement blower vs a turbo in this app is the off throttle and mid throttle boost, which you should recirc or otherwise waste. I'm going to try making a sheet metal intake with 5 TBs.. 4 feeding the cyls and one without an injector that's sprung. I think that should work. This way the blower is never working against itself, working air twice, and I'm wasting the air over the air cooled cylinders. Since the blower is too big for my engine, I think should work satisfactorily. I don't know if I should be concerned about a backfire up the intake though.

Have you looked at an M90? They go for $100 bucks used.

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Andrew M
Onterrible
30ish

Depending on the RPM a M62 isn't "huge".

Remember that they can't be spun over 12000rpm for very long periods of time and are most efficient at lower speeds than that.

The way I look at it - an M62 can flow about 250hp worth of air at peak RPM.

It was "just right" for my 8v 1.8l Golf project. It's almost too small for a 1.6l Honda.

---

Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 1 time(s). Last edit at 04/19/2010 09:06PM by Pete.

Pete Wrote:
-------------------------------------------------------
> Depending on the RPM a M62 isn't "huge".
>
> Remember that they can't be spun over 12000rpm for
> very long periods of time and are most efficient
> at lower speeds than that.
>
> The way I look at it - an M62 can flow about 250hp
> worth of air at peak RPM.
>
> It was "just right" for my 8v 1.8l Golf project.
> It's almost too small for a 1.6l Honda.

I'm putting it on a ~58 HP 1200cc air cooled motor. I still think huge is appropriate.

I thought 16k RPM was more the upper end. At any rate 1:1 will likely be more than enough for the motor.

---

Andrew M
Onterrible
30ish

What about the HP it takes to turn that compressor to waste all that extra air?
Turbo charging adds no extra parasitic drag, and sized right should come on quick enough. How low in the rev range do you plan on running that engine anyway?

How about a boost storage system for instant throttle response?

So where actually talking numbers.

I tried some various formulas that are out there.. and depending on what you assume and what formula, it looks like my engine want's around 230 CFM @ 8k rpm for 6 PSI of boost.

Now these older Eaton Graphs can be confusing, but no matter how you look at it, the M62 geared at 1:1 will give me that.

And now that I think about it more, I think I did read that 14k wasn't for prolonged use.. but I have definitely heard of people talking about 16k.

At any rate, with 1 e rpm : 1.33 b rpm, with the motor pegged at 8k, the blower is eating ~380 CFM, which gives me loads of air for the engine and to waste.

---

Andrew M
Onterrible
30ish

phlat65 Wrote:
-------------------------------------------------------
> What about the HP it takes to turn that compressor
> to waste all that extra air?
> Turbo charging adds no extra parasitic drag, and
> sized right should come on quick enough. How low
> in the rev range do you plan on running that
> engine anyway?
>
> How about a boost storage system for instant
> throttle response?


Turbos do have a parasitic drag on the engine, through backpressure. It's not free boost. My understanding is that the real benefit over a super is the super high RPM achieved via the exhaust driven turbine versus a realistically achievable belt driven combo.

My thoughts are that the super is so big, the engine won't find it wanting at any range in the RPM. It will have all the boost it can handle throughout.

The parasitic loss will be kept in check by A: not making the super work hard by running huge PSI, or crazy high RPM, B: not sucking against a closed / half open throttle (or pushing against), C: by atmospheric wasting over the cylinders I can likely lose the crank driven cooling fan, which at 6k has to be quite a parasitic loss.

---

Andrew M
Onterrible
30ish