twin wastegates

[sophat34]

ok, I know how many people here dont like any thing new or unproven but here goes anyway. I Was looking at magnus's sight and saw there dual wastegate turbo for rx-7's thought to my self cool, huge turbo and no lag. what if we took a larger turbo compressor wheel and housing and coupled it to a smaller sized, say 14b ish, turbine wheel and housing. with a manifold with two external gates u should be able to control the boost. my only thoughts on the negitive side where that the difrence in wheel sizes could still cause significant lag on inital boost but the anertia would keep it going in between shifts provided you bov could vent enough of the air. then again I could be wrong, any thoughts and or ideas?

 

[out there]

what's wrong with one wastegate?

 

[sophat34]

with a wheel that small on the turbin side one waste gate wouldnt be enough to control the boost and would lead to too much back pressure choking out the motor or hidering the preformance potential

 

[out there]

so... you're suggesting that a 60mm wastegate can't handle the flow?

 

[DSMJim]

Have you seen the size of the exhaust housings that are being used on an RX7? THey have exhaust flow comparable to a V8 which is why he uses two wastegates. The smallest turbo you can really put on an RX7 is a straight T4 which is larger than most DSM guys run. I have seen T-88 sized turbos on the RX7 before...

 

[kpt4321]

Stupid ricer philosophy. Two isn't always better than one.

 

[out there]

note necessarily stupid, he might not have known that wastegates are made that large.

 

[SpoOLxExO]

I was reading an issue of "Muscle Mustangs and Fast Fords" and they had an article of a 302 based stroker with a 92mm Turbonetics Turbo. This wizzer throws out enough flow to make 1250-1400hp on a V8 application like this. They had one 35 mm gate right next to the collector area of where the turbine housing ties into all 8 cylinders.
The boost was at rediculous levels when they decided to run the turbo setup, noteing that their boost controller was useless untill they decided to add another 35mm gate, 70mm total at the collector area.

In this case two wastegates was completely nessisary due to the fact they had already fabricated the manifolds and collector before they decided to run the turbo setup. (They started on an engine dyno N/A to see what baseline level they had)
If they had just run one GT sized 60mm+ gate from the beggining, they wouldn't have had to have two.

The bigger the turbo you have, the bigger the wastegate you will need in order to keep the boost at a controlled level.

But in the Rx-7's case, you know Japan...Completely non-conformist ways of tuning and fabrication. The small twin setup is mostly for asthetics..or "Looks" to the layman.

 

[kpt4321]

Originally posted by SpoOLxExO
The bigger the turbo you have, the bigger the wastegate you will need in order to keep the boost at a controlled level.

It's not the simple. More airflow necessitates more wastegate, but a larger turbine side reduces the need. Also, the more boost you run, the less wastegate you need.

 

[SpoOLxExO]

Originally posted by kpt4321
It's not the simple. More airflow necessitates more wastegate, but a larger turbine side reduces the need. Also, the more boost you run, the less wastegate you need.

Right, But to run a big turbo at low boost (Honda application, Rx-7 application) you nessesitate a large wastegate, or in the case of the inquring mind, two of them

The reason you would need to run low boost on an RX7; as in this instance of two small gates, is that the apex seals in a rotary engine aren't detonation friendly at all.

A Big T4, which is capible of moving larger Volumes of air at low boost, over the use of a high boost T3T4, is needed to maitain high horsepower at low boost (Most race rotarys only run up to 19psi on built engines, but with HUGE T4's, making the HP numbers of 550-650 HP attainable w/o blowing the apex seals due to too much boost)

So the twin small gate is mostly a Rx7 thing, or twin aftermarket 6-cyl setup.

Two wastegates on a DSM isnt need at all, plenty of bulletproof single setups out there, like HKS STD on manifold, TiAL 40mm on O2 housing etc.

But, the turbo V8 engine in MM&FF spiked to over 30psi with one blip of the throttle, thankfully they had a fuel system to handle the thirst of an outlaw prostreet car. (6's-7's etc)

When they installed the second gate they were able to keep the boost
to a more tunable level (12-15psi) due to the extra "Waste" venting capacity.

This kinda reminds me of the "Twin Turbo DSM" debate:laugh:

 

[sophat34]

I didnt realize that they made wastegates that large. I guess I should have looked in to that a bit more. I kind of just over looked the exhaust gases produced from a wankle, there more on the lines of a turbin engine than a v8. I have a fair understanding of those becasue I am in the process of putting one in my kit plane. I didnt apreciate the ricer comment though.

 

[SpoOLxExO]

Oh dont worry about KPT, hes just into being a power techno-nerd and has trolled many other forums having to respond to similar "Newby" questions, I wouldn't worry about it.

On a relavant note, the Guy with the Rx7 could have put on a 60mm Gate or equivilant, but that gets up to a grand for a GT spec gate.
Using two small gates gets your overal valve area up to the 60mm area, while only spending about $200 a hit for the twins.

 

[kpt4321]

Originally posted by SpoOLxExO
Oh dont worry about KPT, hes just into being a power techno-nerd and has trolled many other forums having to respond to similar "Newby" questions, I wouldn't worry about it.

You know what? I am getting pretty tired of your bullshit.

You claimed that a bigger turbo needed a bigger wastegate. It was a blanket statement, and an untrue one. I simply corrected you, and added on some additional information.

You don't need to make a huge post about how the RX-7 motor works, blah, blah. They are running two wastegates simply because they have to to keep the boost down, no benefit to power. That's it.

Which means that there is no reason to run two wastegates, as long as one can keep your boost down. There has never been a DSM that needed more than one, which means that it's doubtful anyone here will either.

Secondly, I'm not sure what you're talking about trolling forums. Just because I made fun of your stupid idea to put a Skyline drivetrain in a DSM, doesn't mean that I don't help people. I've helped more people with honest questions on here than you will even know.

I just have a problem with punks like who who feel the need to make "statements" for which you have no basis or logical reasoning.


To the poster: Don't worry about it dude. I was being a prick, it's not worth your time to complain about it. Forget I said anything.

Honest questions are fine.

 

[SpoOLxExO]

!!!LAUGHING UNCONTROLLABLY!!!
:thumbdown

 

[LandoAWD]

Dammit guys.