dand86951

Well, I was curious about the backpressure question that comes up regarding the KKK #6 hot housing in particular, so I put a gauge on my car which has a K27/6. I was surprised that at 14 lbs of boost my backpressure peaked at 20psi. On the street my boost comes up very quick and will get max boost at around 3200rpm. Just another data point. Does anyone have the backpressure readings from a Garett hybrid?

Laust Pedersen

dand86951

By backpressure do you mean the pressure in the cross-over pipe (between the header and turbine)?

I have bought a standard wastegate on eBay, gave it a new valve seat and shims and noticed that the valve begins to open at 10psi and can hold no more than 20psi at max flow from a typical garage compressor. Applying pressure to the top (intake pressure) will make the valve open at 6.0 psi. Without the shims the opening (intake) pressure is 4.5 psi.

I am interested in this, since I plan to “tighten up” the wastegate in a very simple and inexpensive way and knowing the boost/backpressure ratio becomes important with this scheme. More about that later if successful.

Laust

jchaley

Tony

The dyno chart I referenced is not my car. It is some on who lives in colorado that has the same turbo. I have not had mine on the dyno. He had a intake leak that was later fixed and a autothority MAF that is not mapped for the TO4E (that and being at 5000 ft may be the cause of the slow boost build up on his car). I have several turbo cars and the lag at altitude is much worse than sea level, plus the turbo has to work harder to make high boost, But in the end its better than the 20% power loss the NA cars have at 5000+ ft (it is really bad at 10000 ft)

john

John

TonyG

jchaley

He must have had one hell of an intake leak!

What ever it was, his turbo came on real late for a basically stock car. Heck... that's where my turbo whips... but for me with my extensive modifications, it's worth it since I make peak HP at 7,000rpms.

For a basically stock car to whip on that late, and roll off at <5700 rpms, makes no sense, as the area-under-the-curve is way too small...


TonyG

Mark Szalaiy

cpt. koolbeenz, The statement I made about the TO4B flowing more than the TO4E was from my research on compressor maps at various web sites .
When you take a 40, 50 , 60 etc, trim wheel , the TO4B flowed alot more.
Go to some sites and see for your self. I talked to David Lindsey yesterday and he said his engineer said the TO4E is bigger and runs a couple pounds more boost.
Every other person or mag. also said the TO4E was the big horsepower turbo. Maybe Tony G. can answer this , he knows alot about turbo's.

Mark

Mark Szalaiy

Also, the turbo I'm using is a TO4B w/ 60 trim and a KKK #8 hotside .
It flows 785 cfm's @ 1 bar ( 56 lb/min) and has the possiblity of making 560 hp ( of course not with my #8 hot housing).

cpt_koolbeenz

TonyG-
I emailed you, PMed you, and called you... Anything else to try? :P

Do you still have your turbo for sale?

cpt_koolbeenz

I was also told by Majestic that the number 6 hotside with the t04e would also have too much backpressure.

I found this online here:http://www.turbonation.com/turbo.htm

A good rule of thumb for when there is too much back pressure is when the pressure in the exhaust manifold is more the half of the pressure in the cylinder. So basically, a larger A/R ratio will improve your engine's top end, while losing some mid range power and increasing turbo lag. A smaller A/R ratio will help the bottom and mid-range, but may effect the top end.

Matt H

Cpt - give gatorbait a buzz, I think he is considering parting a new vitesse kit. If so that turbo would probably suit you fine. I know he needs money now so it might make a good buy. I told him to get with you as well, figured it couldnt hurt.
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dand86951

Yes that was the pressure measured at the CO test port in the crossover.

Rob

After I recieved my Turbo from Majestic (TO4E-46 with a #6 hotside machined out for a stage III turbine wheel), I had the opportunity to compare my modified hotside to both a factory #6 and #8 hotside. The #6 and #8 hotsides are the same (same A/R ratio) except for the exit port hole size (exducer size for the turbine wheel) and the corresponding interface of this hole with the cross sectional area (forms a radial slot around the turbine wheel where the exhaust enters the turbine wheel). When a factory #6 gets machined out for a stage III wheel, you end up with an exducer size somewhere in between but very close to a #8 (the turbine wheel sizes I found are as follows #6 = 1.969", #8 = 2.303, Turbonetics Stage III = 2.229 - NOTE: these are the exducer wheel diameters only)

cpt_koolbeenz

Good point Rob... I will ask Majestic about that.
What does it mean when half of the pressure in the cylinder? For exhaust or boost?

Where exactly is the test plug for the exhaust- I think it may be leaking?

Thanks

cpt_koolbeenz

Thanks Matt - good idea - hopefully he is easier to get a hold of than Tony

Ahhh - "It feels good to be a" member. Just payed - how long till it shows in red?

TonyG- Gave you another ring... Turbo, is it still for sale?

TurboTommy

What do you mean by "half the cylinder pressure"? Average cylinder pressures could be 100 psi and when it's burning, it's alot more than that. So, that can't be what you mean.

Turbine dynamics are much harder to understand than the compressor ( CFM rules; that's it). In a nutshell, all that's important is the back pressure vs boost pressure. If back pressure is less than boost pressure, you will make good top end power. Im still trying to figure out if some valve overlap is needed to make the most use out of this concept. Tony, did you ever get your back pressure tested?

cpt_koolbeenz

Can't get a hold of TonyG - does anyone have an upgraded turbo they want to sell before I send mine to Majestic?