a/r numbers

sventek · Post by **sventek** » Sun Feb 10, 2002 3:12 pm

I am trying to pick out a correct turbo for what I want. I have a 1776, 110 cam...etc.. I am looking at the t-25 or t-3. I understand that the lower the a/r, the quicker it spools up in low rpm's, right. I just want to be on max boost at about 4500-5500? I guess I am just asking what are some of the driving characteristics of some of your turbo engines close to my setup..thanks

sventek · Post by **sventek** » Sun Feb 10, 2002 3:15 pm

ok, sorry if that last post was kinda vague. My wife rushing me!! Anyhow.
I have only seen a turbo vw at the strip. I have never driven one or riden in one. So I have no basis to make my decision based on my wants, ya know? I would just like to know whats the best rpm range is for the turbo to be performing near max boost. I usually shift at 5-6000 r's, just depends. Motor handles it very well. I will also be using john copper head gaskets when lowering my c/r...which I gather, bout 7.5:1 is a good figure? I would like to run 10-15 psi on the street.
thanks guys
I am a confessed lurker, but most my questions get answered by existing post....look forward every day to checking in!

Jean Melim · Post by **Jean Melim** » Sun Feb 10, 2002 3:46 pm

hi...
you have a counter weighted crank?
the turbo t3 is ok for the rpm range, that you chose.
know, one question. You go to blow trough or draw trough?
one carb, two, or fuel injection?

Jean

Sidewalk · Post by **Sidewalk** » Sun Feb 10, 2002 3:50 pm

Just remember that a turbo is not RPM reactive, it is load reactive. 5000 RPM in first gear has less load then 5000 in fourth.

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'59 bug-unstockStella
'88 Bronco II-unstock Sonja
"Yes, I am a smart ass."

volksnut · Post by **volksnut** » Sun Feb 10, 2002 7:28 pm

then what would you all shift at..first gear 4500...mine will wind to 6000 but would it be better to get in 2nd quicker?

panel · Post by **panel** » Sun Feb 10, 2002 7:58 pm

<BLOCKQUOTE>quote:<HR>Originally posted by Sidewalk:
Just remember that a turbo is not RPM reactive, it is load reactive. 5000 RPM in first gear has less load then 5000 in fourth.
<HR></BLOCKQUOTE>

I don't even see boost in first just late in 2nd and lots in 3rd when theres lots of load forth in the bus under full boost is too fast for me in the van.

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Turbo powered split window bus http://www.geocities.com/panelvan65/panel1

sventek · Post by **sventek** » Sun Feb 10, 2002 8:55 pm

Yep, I have a c/w crank, everything is balanced. i like the sound of what panel said for his setup. How big of a difference is in the t03 and the t-25, in all aspects. I am planning on blow thru as it seems to be the easiest to set up as far as plumbing and turbo placement (under the tin, hideaway). I just need to figure out a carb setup. I am now running dual dell 40's normally aspirated. I really dont know if I should go duals or not with the turbo. I am thinking of just going with one of the 40's, just up the size of the venturies. I seem to see more blow thru with duals and draw thru with singles? Must mean something.
Also, 'bout how much does it cost to get a dell/s fixed for turbo?
thanks

Sidewalk · Post by **Sidewalk** » Mon Feb 11, 2002 9:18 am

<BLOCKQUOTE>quote:<HR>Originally posted by panel:
 I don't even see boost in first just late in 2nd and lots in 3rd when theres lots of load forth in the bus under full boost is too fast for me in the van.

<HR></BLOCKQUOTE>

In my last turbo car I could pull full boost in first gear, easily. I have pulled boost without even moving in that car.

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'59 bug-unstockStella
'88 Bronco II-unstock Sonja
"Yes, I am a smart ass."

uh wrong! · Post by **uh wrong!** » Mon Feb 11, 2002 1:37 pm

<BLOCKQUOTE>quote:<HR>Originally posted by Sidewalk:
Just remember that a turbo is not RPM reactive, it is load reactive. 5000 RPM in first gear has less load then 5000 in fourth.

<HR></BLOCKQUOTE>Originally posted by Sidewalk:
In my last turbo car I could pull full boost in first gear, easily. I have pulled boost without even moving in that car.
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'59 bug-unstockStella
'88 Bronco II-unstock Sonja
"Yes, I am a smart ass."

@@@@@@@@@@@@@@@@@@@@@@@

Like YOU said, a turbo is load reactive.

How the hell are you pulling full boost without even moving??? DUH!!

You cannot create a load by standing still.

You should add this to the bottom of your sig.

AND
"I'm a DUMBASS too"

MagOO · Post by **MagOO** » Mon Feb 11, 2002 2:18 pm

I have heard of instances where cars were making boost at the line...are you saying it is impossible to biuld boost WITHOUT the car being under load? Say a car with a relativly small a/r ...could it not speed the hot exhaust gasses fast enough and with enough energy to build some positive manifold pressure? Not a flame just a question...

Sidewalk · Post by **Sidewalk** » Mon Feb 11, 2002 2:21 pm

Ah, how sweet it is to talk trash without an identity. I think I will add that to my sig line.

However, when was the last time you did a burn out? That was a load.

Have you ever heard of a trans brake? That is to build up a load without going anywhere.

In my case, I held put on the parking break, and got the wheels spinning, without dropping the clutch. So there was not any inertia to keep the RPM's up, I had to build power using boost by letting the clutch slip with my foot on the gas until there was enough poewr to do it.

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'59 bug-unstockStella
'88 Bronco II-unstock Sonja
"Yes, I am a smart ass."

Sidewalk · Post by **Sidewalk** » Mon Feb 11, 2002 2:24 pm

<BLOCKQUOTE>quote:<HR>Originally posted by MagOO:
I have heard of instances where cars were making boost at the line...are you saying it is impossible to biuld boost WITHOUT the car being under load? Say a car with a relativly small a/r ...could it not speed the hot exhaust gasses fast enough and with enough energy to build some positive manifold pressure? Not a flame just a question...<HR></BLOCKQUOTE>

Just idling is a load, but not much. If set up properly, you could build boost under the conditions you are thinking, but it would be useless at the higher end. There would not be enough exhaust flow.

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'59 bug-unstockStella
'88 Bronco II-unstock Sonja
"Yes, I am a smart ass."
"I'm a DUMBASS too"

But are you gutless?

Searoy · Post by **Searoy** » Mon Feb 11, 2002 2:50 pm

Hearsay:
Muffler Mike told me that when he ran Jim Hagerthorne's (sp?) 1915 turbo motor he would build 5 lb boost at the line, just on the rev limiter.

That said, it was boost in the intake manifold. The heads were unported 044s with 40x36 valves. You CAN build boost at the line under no load IF there is a flow restriction between the turbo and the intake valve, such as a stock port. If those CB heads were given a mild to moderate port job, the boost I'm sure would go away AND performance would improve.

The important thing is how much fuel/air mix is getting into the chamber? I'd rather be running 15 lb of boost and get 180% VE than run 25 lb of boost and get 185%.

Boost numbers are relatively unimportant without regard to intake passage flow rates.

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*** Teach a Man to Fish ***
Searoy

"I tend to lean toward a tighter gap and a
looser skirt....a little slap never hurt." -- Joe of the West

Sidewalk · Post by **Sidewalk** » Mon Feb 11, 2002 3:45 pm

Good point, I didn't think about that.

------------------
'59 bug-unstockStella
'88 Bronco II-unstock Sonja
"Yes, I am a smart ass."
"I'm a DUMBASS too"

But are you gutless?

Marty · Post by **Marty** » Mon Feb 11, 2002 5:37 pm

Ahhh, now you are getting to the secrets of launching turbo cars. When its on a rev limiter (like a two-step) its getting loaded up. I think the odd firing going on gets the exhaust pulses going stronger and spins the turbine faster. I am obviously not a teacher. I launch at 6000 rpms on a two step with my foot to the floor and my engine sits very hapily at 6 pounds of boost until I let the clutch out.
All big HP turbo guys that I have seen (including V8's) launch on a limiter.

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Marty Staggs

www.staggsracing.com