Thats what I believe whats happening. Here's another example:

Take a stock Fd thats boosting 10psi now take another Fd, do everything necessary to increase the engines ability to breath, then try to run that same engine at 10psi on un-modified turbos. The modified engine will make more hp at the same boost level as the stock engine but, do we accually know how much harder the turbo is working to keep up with the increased flow of the modified engine? It's odvious that the turbo would have to work alot harder to keep up with the demand of the engines higher flowing capabilities therefore taking it out of it efficiancy range.

For all we know Red's older turbo could have been boosting 30psi just so that 14psi would reach the manifold?

 

Red's engine (built by Marcos Acosta) was built to support over 1000 hp. So it has other mods besides a ported engine to allow for his engine to breath and make that kind of hp with a large enough turbo. His engine flows so well that the turbo can't keep up. Thats my opinion.

 

Here is the dyno and video:

http://home.comcast.net/~mhaun5/rx7/RedRx714PSI.wmv

and



The only thing about my math that could be wrong, is that the 1.92 cfm does not equal 1 rwhp.

 

I just spoke to Innovative Turbo agian. I am sure they are loving me call so often, but here is the bottom line:

- If the engine is indeed flowing 83/84 lbs/min
- If the compressor is indeed a T72
- If the turbo pressure ratio was actually 2.0 or abouts

*THEN THE RPM SHAFT SPEED WOULD BE AT 100,000 RPM OR HIGHER*

With regards to the wastegate being open, the wastegate only knows psi pressure; not velocity. Take for example at 4000 RPM's. The wastegate was open at this point, and continues through the map range. The pressure in the manifold for the wastegate never changes, for it is past the spring rate and is open. Yet, the velocity is still increasing through the RPM band. This is what accounts for more horsepower at 6000 RPMS vs 4000 RPMS. Remember, PSI is the same, velocity is different (more at higher engine RPMs). This remains true until the engine cannot breathe anymore until more PSI is given.

So, at the pressure ratio I was running, the engine could only flow at a maximum velocity equal to 84 lbs/min.

It is Innovatives professional reason that the shaft speed was the cause for the turbo failure. The engine is moving more air than the compressor was designed to handle.

 

Because you delayed answering what was a simple question about peak volumetric efficiency vs. torque curve by first giving a remedial lesson on where the torque and horsepower curves cross. Certainly thoughtful, but totally irrelevant to the question or its answer.

 

i've got reservations about their port velocity explanation too, but that's beside the point. my biggest thing is how are you spinning the turbo faster without building more boost? it's the basic premise of any forced induction system, the faster you spin a compressor the more boost it builds. w/ a turbo that's accomplished by spinning the turbine faster, w/ a supercharger it's accomplished by spinning the belt faster.

 

That's true up to a certain point. The CFM is static on the engine side and compressors are designed for certain "ranges" above which the flow curve drops off substantially. It's not a linear thing whereas the faster you spin it, the more boost you make. I'm sure there are more advanced aerodynamic and thermodynamic pricipals that apply above a certain point and that I'm not qualified to elaborate on. And as you mentioned before, the air heats up tremendously beyond a compressor's efficiency range. It's the flow rate that's important here, not the psi. One can have 50cf of air @15psi and one can have 85cf of air @15psi. Go past the compressor's "range" and it cannot "flow" the cfm required (and determined by the engine) to hold that 15psi or whatever number you'd like to throw in there.

 

I suggest that you give Innovative a call to answer your questions. What I had stated is how it works, based from the numerious conversations I have had with them.

PSI isn't dependant to engine flow in a static form. Two different engines can run the same boost at different CFM levels.

 

Simple. The Engine is sucking up the air faster than the turbo can compress it. The Turbo may be spinning at the proper speed (for example) to produce 80lbs/min of air at 10psi, but if the engine is trying to suck up say 90+ lbs/min of air, then the turbo can't keep up. The Turbo will constantly work in a vacuum on both sides. Simply put, the turbo can't flow enough air to keep up with the engines demands.

If u look at the graph Red posted with the plot, you can see that at the same compressor RPM, it can create varied levels of pressure/flow. The amount of work the turbo does is very depandant on the engines ability to breath, the more it can breath, the harder to the turbo has to work.

 

look, you're wrong stop trying to insist otherwise. no matter how much the engine is sucking in, it cannot impart it's flow needs directly on the compressor. for the engine to actually spin the turbo from the intake ports would necessitate it be under vacuum. how can the intake manifold be under vacuum and 10lbs. of boost at the same time?

 

FD Racer:
Well fortunately for me I'm right. Unfortunately I've run out of idea's to explain the situation to u.

All U need to do is look at the compressor map, it shows that it should not be trying to force 80lbs/min at 10psi, because it would be spinning at 100,000 rpms, creating to much heat. And thats exactly what Red had done.

 

we're going in circles here, i know as air gets compressed it becomes harder and harder to compress it even more. it also heats up at an accelerating rate as it gets more and more compressed. but we're not talking about 40lbs. of boost here, where more boost just nets you diminishing returns. it's running at 10lbs. of boost. if the shaft speed limit for this turbo is say approx. 100k rpms, and it has to already spin at that rate to make 10lbs. of boost, then this turbo is only able to make 10lbs. of boost max. what 72mm turbo have you seen on any application be able to boost only 10lbs? what if red wanted to boost 20lbs. on the t72, he obviously can't spin it any faster, so does that mean it's maxed out at 10lbs? just look at the stock 20b turbos, they're tiny. if this huge turbo gets overspun at 10psi, then those things will self destruct at the moment any 20b hits boost. i know red's motor is ported but, c'mon it won't make that much of a difference.

i don't mean to contradict what everyone else is saying, i just find this topic pretty interesting. i've just never seen or heard of any other situation like this. i've got scores of data on similar sized turbos from datalogs of several drag cars, so i'm familiar with the capabilities of these turbos. if anyone has seen any other cases where a 72mm turbo has been totally overwhelmed at 10lbs. of boost and just died from overspinning, please let me know. sorry for the thread jack.

 

FDRacer, you can run 84lbs/min @ 10psi. You don't need boost to run the turbo that fast. Call any of the turbo shops, they can explain. Its about velocity from the engine flow.

 

We posted that at the same time. How many of the other engines flow 84lbs/min that you have seen? I have given a few people rides in the car, and a few were even at the dyno. Unless you can prove that the 1.92 cfm = 1rwhp is wrong; then it indicates it is flowing at 84lbs/min.

Innovative Turbo has already said that regardless of the boost, if the engine flows that, then it will overspin the turbo at that airflow.

 

I believe a 72mm turbo is to small for a ported out 20B making 600+ HP. It would take a larger turbo than that to make 600HP on a 13B! (please don't shoot!)

That is why i am glad i have a GTB 88 coming this week from Innovative!
To big? Never underestimate the flow capabilities of the rotary!

If the turbo was trying to keep up with the flow rate of Red's 3-rotor and was not able to meet the amount of boost it was set to the waste gate would have never opened....

That would be fine as the turbo would just max out, being out of its range of operation....but if the exhaust AR was to small it would just cause the turbo to keep on spinning and over rev!

I think if you had a larger exhaust AR it would not have prematurely self destructed, but simply maxed out...

Just my 2-cents!

 

>I just spoke to Innovative Turbo agian. I am sure they are loving me call so often, but here is the bottom line:
- If the engine is indeed flowing 83/84 lbs/min
- If the compressor is indeed a T72
- If the turbo pressure ratio was actually 2.0 or abouts

*THEN THE RPM SHAFT SPEED WOULD BE AT 100,000 RPM OR HIGHER*<

-Nope, engine is NOT flowing 83/84lbs/ min or else it would show up at the wheel on the dyno !!!!
- T72 or not...... ITS should be able to tell.....
-Boost ???Only those present at dyno run(s) will know.

Anytime you hit the choke point or maximun flow rating of a turbocharger it will boost drop at higher rpms......effiency is out the window....and you're simply heating up the output.

Red: Do youck have a dyno run with torque ?
I have much respect for your car and yourself.....600+rwh is something many dream of:-) ...so don't take this as an attack on your numbers.
Somewhere your numbers are off....or you're being mis-informed since your turbo was fairly new before failing.

1.92cfm=1 hp sounds wrong......maybe ~1.45cfm or ~1lb for 10 hp (roughly)
Theoretical answer=> CFM*.069*10= max hp for given turbo.

82lbs=(82*14.473) 1187 cfm

1187cfm*.069*10= 819 hp

Hope this helps.....
Back to topic:-)

JD

 

JD-

Those "ifs" were stating just as the static figures.

I was at the dyno, and so was a bunch of other people too. You can call Marcos Acosta SR or Jr, along with some of the other people that work there.

The turbo is also a T72, again, I was just saying that in a retorical sense. And we only 100% know what the boost was at the manifold, not at the turbo outlet.

Read that link I sent you. Hopefully howard coleman or some of the other turbo guys can come in and speak to the cfm calculations.

 

Thats the thing. It all depends on the flowing capabilities of that particular application. I know "thedguy" and "Red-Rx7" are running out of examples but I have another to help you understand what they're trying to say. This is just the way I visualize things.

I will use the stock 20b twins as an example. Take the stock twins of a 20b and run them at 10psi on a 20b (which is technically a 4.0L engine because of the way it breaths). Now take those same twins and stick them on a 8.0L Viper V10(which is roughly twice the displacment of the 20b) and try to get these same turbos to move enough air to create 10psi manifold pressure. It's not going to happen because the 8.0L V10 is going to suck down twice as much air as the 20b. This will cause the twins to run way out of it's efficiancy range just to get up with the twice as large engine. Does that make any since to anyone?


You only have boost if the turbo is out flowing the engine at that particular time. In Red's case his engine quickly starts to out flow his turbo.

 

I got in the Tremec today for test fitting..

Liberty transmissions was kind enough to put me together an empty case to use for test fitting...
The fittment is perfect other than the fact that i have to use a spacer to get the shifter in the right location and also have to fabricate a trans crossmember!

I ordered the real deal today and it will be in about 3 weeks! Hopefully the same time the Browell bell housing will be done!

Tremec 3556 TKO from liberty transmissions with syncro 1st, 5th and reverse only!

 

Also in the mail came my twin clutch setup which might be changed for a push type if i can get some issues worked out with the bell housing in order to install a hydraulic bearing assembly!

 

Any one know where i can find a block off for the oil metering pump for the 20B...

I am sure i could jigsaw one out but i am looking for something a little more professional!

 

just make your own, bolt it on there, then trim it down perfect with a dremel. you can't get any more professional looking than that.

 

What made you go with the Tremec TKO?

I get my GURU box next week!

 

I guess i ment easier not more professional! Just being lazy..... I know what to do with it and i have plenty of scrap aluminum laying around.....

I just thought if i found someone with it in a program they could jsut push a button and $15 dollars later i am bolting it on!!!!

 

The Guru box will not hold as much power as the week point of the trans becomes the stock case! It tries to split itself apart!

The other reason is the GURU box has straight cut gears and not very good downshifts!

Have you ever heard a street car with straight cut gears? (very loud and the shifts sound like the bottom is droping out!)

The TKO trans is tough stock but the syncro's don't like to shift above 7000RPM or so.

Liberty makes the trans with stronger gears, an alternative to the syncros and can custom taylor it to suite your needs.(i am having a custom input shaft made)

I chose to keep the syncro's in first for the obvious and 5th since you are normally not shifting into 5th real hard!

2nd through 4th have face plate engagment in place of the syncros which i don't want to try and explain in detail but it ensures that you do not miss a gear as it helps pull it in! You could shift clutchless however they do not recommend it! Down shifting is not supposed to be to bad however you can not beat a syncro tranny for that!

Also i figure with the torque the mustand and camaro guys are making and the extra weight of the cars..........if these transmissions can hold up to that abuse than they can handle a lighter car with less torque and never break!

So i hope...........