ASE_Joe

I was just curious as to the largest pipe diameter (external as well as internal) for the FC. What kind of clearence is there with a 3" pipe and the drive axles? I am thinking of going with a 4" for my setup, and was wondering if i should use 2 race bullets with a 4" ID and dump it at the rear of the passenger door, or try to get it run all the way to the rear?
Thanks,
Joe

ASE_Joe

ttt

bcty

i think 4" pipeing will be fine but i think 3" wouldnt make much diffrence if u went that route...

NZConvertible

A 4” dump off the turbo is a good idea for minimising backpressure immediately after the turbine exit, but really isn’t required for the whole exhaust. And while the pipe might fit under the car, the mufflers probably won’t. Cone down to 3” before the first muffler. I hope you're running a serious external wastegate for this. You'll need it.
Also, check the legality of side pipes where you live. Over here, side pipes must exit from under the car at least 300mm rearwards of the passenger openings, which is impossible on an FC!

ASE_Joe

Jason,
The wastegate is a 40mm HKS unit for now. I will be venting to the atmosphere. I am running a T04E .70/1.15 divided. P-Trim with a "Rice Racing" street port

This is why i was thinking 4". I would think that the exhaust side would help to make up for the wastegate flow, but i am not 100% sure on this.

ASE_Joe

bump

RETed

The wastegate is too small.&nbsp Couple that with the large exhaust system, everything = boost creep.

A 3" exhaust system can easily support 500hp - I'd worry about getting larger wastegate than spending the money on the 4" exhaust system.



-Ted

ASE_Joe

Well are there any formulas out there to figure out which one i would need? Is there a such thing as too large a wastegate? I would assume there is....but not sure.
How about the 50-60mm HKS gates? Would that work?
Thanks,
Joe

ASE_Joe

double post, stupid dialup

RETed

Not really, but there are "rules of thumb".

No such thing, if you can believe it.&nbsp In this case, bigger is always better.

I always recommend a 46mm Tial or 50mm HKS minimum for all T04 full turbo upgrades.



-Ted

BLUE TII

iTrader: (9)

Can you run dual WG? I always see tubular mani.s having long passages to a single WG, couldn't you run two smaller ones off each manifold runner and do away w/ alot of tubing? Yeah, 2 WG cost more, but if you already have 1...

RETed

Sure you can run two (smaller) wastegates, but that's a lot of extra piping and space for the extra wastegate...&nbsp I'm not against the idea, but it's gonna take a miracle to fit all of that in the engine bay.&nbsp If you do pull this off, post some pics for us!


-Ted

BLUE TII

iTrader: (9)

Well, I wasn't going to run external WG; and frankly I am a bit worried about it right now.
What do you think. T04B 60-1 compressor upgrade stock S5 turbo w/ "O" trim exhaust wheel. 3 1/2" straight through exhaust, large street port. I want to run low boost- just looking for around 300RWHP. Think it will creep at top of 5th? I will run a pop off valve, but don't want to toast the turbo too soon.

ASE_Joe

thanks for the advice Ted!

Maxthe7man

Sorry Ted, but I have to disagree with you on this stuff, after building a stainless manifold, piping individual gates is easier that running one off both pipes..
Also the wastegate size and flow is not the same among all the manafacturers, the Tial gates often outflow the competitors gates of the next size up, and I have that from the horses mouth..
I have been reading some Australian speed mags, the gate of choice over there is a 40mm on a 13bt with a to4e , some are even running smaller gates than that, even 20 b's with t-78's and what not run 42mm gates... There is such a thing as too large a wastegate as well, where the valve is operating to close to the seat and starts to hunt and response is slow..
There is no real flow charts for wastegates, its unfortunatley trial and error alot of times, and thats to bad really, but calculation the flow reuired to control boost on a give motor with a given turbo would also have the variable of manifold design to contend with as well as wastegate exhaust piping and pressure drop, not to mention dealing with varied compressor speeds..
40mm will work fine...Max

RETed

This is highly dependent on design.&nbsp A collected turbine section would allow for merged turbo exhaust manifold runners and therefore would allow for a relatively easy, single wastegate pipe.


I recommend Tial 46mm or HKS 50mm wastegates minimum.&nbsp I tell all my clients that, and this is what I would recommend if anyone asks me.


You can quote all you want.&nbsp I consult with a chap that runs a 9-second RX-3 who is knocking on 8's very soon.&nbsp I have direct correspondence with this racer, and we talk a lot of about wastegates and wastegate design.&nbsp He runs an HKS GT 60mm wastegate with no problems.&nbsp I'll stick to my experience over your reference material.


You can do whatever you want; I'll stick to my rules of thumb.&nbsp I have never had anyone have any trouble with my recommendations, and no one has run into any problems with boost creep.&nbsp If you can run a 40mm wastegate, then I call you lucky.&nbsp There have been numerous folks in the Single Turbo section that have tried 40mm wastegates, and many have experienced boost creep.&nbsp Your references have all been magazine material (up until this point), and I don't see any direct experiences with wastegates in general.&nbsp All of your "claims" have already been refuted in my experience, so I'd rather stick to my experiences...thank you very much.



-Ted

RETed

If you're sticking with a compressor upgrade, then it's implied that you're keeping the stock turbo exhaust manifold.&nbsp It isn't very easy to retrofit an external wastegate onto a stock turbo exhaust manifold, especially with a Kouki turbo divided design.&nbsp I know tims has done this, but it's not something a "backyard mechanic" would have the tools to attempt.&nbsp I've never had problems with my stock Zenki turbo, but it does have a clipped stock turbine wheel.


-Ted

BLUE TII

iTrader: (9)

Ya, the guy doing my turbo apparantly puts external WGs on his S4 upgrades. I will hope for the best :-)
I have read a turbo w/ flat backing plate behind the internal WG (like all the FC downpipe applications I have seen) have more of a chance for boost spiking/creep than if the downpipe incorporated area behind the WG. Think its worth it to have my stainless downpipe modded to incorporate a backing plate w/ WG relief area welded on the WG side of the pipe?
I guess if I waste the turbo overspining it via POV I will have to go full T04

Maxthe7man

Of course, the reasoning for 2 tubes merged would only be seen on a divided manifold, however after building several, i can say its easier to build them with two gates rather than a twinned pipe to one... Sit down with a Tig welder and chop saw for a couple of hours and you will see what I mean...[/quote]




The tial 40 mm gate outflows the larger HKS gates, a tial 46 mm gate is huge..



And whats used on 9 second drag car is far different that a street driven Rx-7....Overly Large valves due not track that well in controlling pressures, trust me Ted, I have worked with more valves of various types than you have hairs on your head...


You mean stick to their experiences with using manifolds that are or may not be designed that well in the first place... An overly large wastegate is a crutch for poor piping design...I've seen some of those setup ted and the piping is horrendous enough it would probably creep with a 90mm wastegate... I think some people just have wastegate envy...Max

ASE_Joe

I personally dont care what the Wastegate is. I bought the HKS unit at the time simply because i got a good deal on it brand new. Also at that time, i was actually planning on going the cheap route with my car. Stock ports, T04E, HKS cast manifold and 40mm wastegate, AIC, 3" DP mated to the 2.5" duals on the car now.
Now, thanks in part to Relvinnian, I have come to my senses and have decided to do the car correctly.

My manifold will be custom, and i am thinking that the power peak will be somewhere around the 6500rpm range.... As for the wastegate size, I was thinking 50mm (as RETed originally said) but i cant do anything until someone buys my manifold and gate.

RETed

I would love to see what your idea of "efficient" turbo exhaust manifold (and wastegate piping) design - got some pics?


Sorry, that doesn't apply to me - I don't build my cars to impress anyone from their looks.



-Ted

Maxthe7man

Yeah I know, I've seen your car........
Yeah there are some pics of my manifold in the single turbo forum, if I remember right its in a post about manifold pipe size...
I looked at alot of manifolds before building mine, I had an HKS one to study as well. most of the design were relying on high amounts of back pressure to induce wastegate flow..
I also noticed that when they cut into the pipeing on some fof then, they did not get the wastegate pipe connection full size, the pipe itself was larger than the actual entry into the pipe, if you are going to use 1.5 inch tubing, make the connection to the main pipes 1.5 inch, most used 1.5 inch pipe saddle welded over a 1" hole...
The next one I build is going to be twin gate manifold, I really want to see if there is a difference between a true divided manifold and a divided that has the wastegate lines merged, this has been a point of contention in the STF a couple of times..
I know adding elbows creates a trap in a duct which stops sound waves and pulses, I built a bit of this into my manifold in attempt to stop any pulse mixing..However not sure though if acoustical laws will have any relevance in a turbo rotary, but its worth a try....max