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Resident Ford Nut
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Discussion Starter #1
What determines the rpm limit on a turbo engine?

A built 500" engine with good heads and a solid roller what determines how fast you spin the engine, where does turbo size or restriction come into play?

I guess the question is: can you spin a 500" turbo engine 8,000?

S CP :)bulb
 

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What determines the rpm limit on a turbo engine?
I guess the question is: can you spin a 500" turbo engine 8,000?

S CP :)bulb
No way in hell. Well, maybe for a little while.:D
Back in the late 60's the Indy guys where just a bunch of Hot Rodders, and not the geniuses they are today. So they didn't know that.

And the Europee-ons are to to snooty to even bother listening to such stuff.




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Resident Ford Nut
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Discussion Starter #3
I think the Renault's turned 14,000 :)bulb

on a 500+" engine is the limiting factor the size of the turbo(s) or at least what's commercially available to handle 8,000 rpm flow from a 500" engine?

S CP
 

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Highaboosta
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I don't understand your question.

When I had 37% gears it would put it on the rev limiter at 8000 rpm.
So I changed gears to 60% and pulled it down to 6800 rpm and gained performance.

Proper size turbo's are not going to limit the rpm if that's your question.
It was just way past the max torque range. Still is.

Does anyone make a jet pump that can hold 2000 ft lbs tq at 6000 rpm ?
 

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Owner/Crew Chief
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Does anyone make a jet pump that can hold 2000 ft lbs tq at 6000 rpm ?
That equates to just under 2,286 Hp which any decent Blown Alky motor can make ... Both AMT & Dominator Pumps can, and have handled that Hp with the proper shaft and bracing of the suction pieces.
 

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Highaboosta
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But can those pumps load it down enough to hold it to 6000 rpm ?

Haas just went to one of the high helix impellers and I think he's turning that 7200 with around 1650 hp / tq.
 

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Discussion Starter #8
I don't understand your question.



Proper size turbo's are not going to limit the rpm if that's your question.
?
in a nut shell that's the question....then you need to control lag if the turbo's are designed to spin 8,000 they might be a bit slow from 3,500-4,500.

S CP
 

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A 'Big' Hi-Helix could be cut to hold a bigger Hp motor to around 6,000 rpm but I have no idea why someone would want to do that given the flow characteristics of today's jet pumps.
 

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Highaboosta
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in a nut shell that's the question....then you need to control lag if the turbo's are designed to spin 8,000 they might be a bit slow from 3,500-4,500. S CP
That's not really how it works. It's based on load more than rpm with turbo's.
If you can apply enough load you can make maximum boost at 3500 rpm.
That was how he dynoed my engine. It was WOT and 28# boost at 3500 and then he lets the water out of the brake to let it rev up and records the torque curve. It made max torque at 4800 rpm.

 

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Discussion Starter #11
Mark that dyno sheet is just nuts. I'm going to print that and have as a goal to match one day. :)grn

So when you were spinning it to 8,000 what power do you think it was making? And why is the peak trq number so low, is that a function of the cam or turbo size?


S CP :D
 

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But can those pumps load it down enough to hold it to 6000 rpm ?

Haas just went to one of the high helix impellers and I think he's turning that 7200 with around 1650 hp / tq.
could easily be done the same way you did it. just use an amt AA and an owens gear to underdrive it. it'll hold it down to whatever you want to hold it down to, and hold together just fine...

if you had no gear ratio options, how big of a prop would you need to hold yours down to 6000????
 

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Highaboosta
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Mark that dyno sheet is just nuts. I'm going to print that and have as a goal to match one day. :)grn

So when you were spinning it to 8,000 what power do you think it was making? And why is the peak trq number so low, is that a function of the cam or turbo size?
S CP :D
Well the hp and tq kept dropping as the rpm went higher on the dyno sheet, probably because I didn't get the heads ported out. :D
It was hard to tell in the boat. It just kept pulling. The midrange is pretty impressive.

I suppose a bigger cam would change the torque and hp peak. I would much prefer to keep the rpm lower and the stresses lower.
I haven't had any valve train problems and still don't have a stud girdle. Looking for taller gears to pull the rpm down lower yet.
 

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Sleeper, your looking at turbos in kind of thewrong light. Unchained says as much, without actuallu saying it. There is no need to spin a turbo motor that hard. Turbo boost, therefore power, is a product of load, not RPM. Up to a point, the more load you put on the engine, the more boost it will make, secially at lower RPM. The faster the engine spins, the more air it ingests. With a roots or centrifigul the air is 100% tied to engine RPM. Even worse, with a roots, the boost pressure is indenpendent of RPM. Air flow goes up with RPM, but so does the engines demand. They are pretty much locked together. A centrif moves more are with RPM as well, but alos has a boost curve that you try to match to the needs of the application . Off idle WOT boost with a centri is dismall, but gains as the blower speed increases, but is still linked to engine speed VS blower speed.

With a turbo, there is no direct RPM link. Its link by load. Load it, and the boost takes off. Take the load away, and the boost drops, even at the same RPM.
There is just no reason to spin the hell out of a turbo unlesss the class, like Indy and Formula 1 restricts the boost pressure, or the engine just can't accept any more pressure.
The reason the Offy was so dominate at Indy was they had no limit originally. It died when they imposed one.

If GNs didn't have a boost limit, no one would run a GN engine above 6500, maybe even lower, but we would all be making more power then we do.



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