http://www.pro-flo.com/proflo_3in_egt_egt_gauge_kit.htm

this has me thinking. I was just going to run one egt after the turbo but after that link it really opened my eyes to just how important it is. This gauge has dual probes and reads it off of only one gauge. good gauge?

 

rotaries really need an exceptionally unrestrictive exhaust V piston engines.

when comparing downpipe sizing it is important to consider the formula for the area of a circle since it includes squaring the radius... that means a 6 inch pipe has more area than just 2 X a 3 inch pipe.

assuming pipe size is O D and we are solving for I D and using a .065 wall

2.5 inch O D has 4.41 sq inches of area

3 inch O D has 6.47 notice you are up 20% in diameter but 46.7% in area!!

3.5 inch O D has 8.92 up 42% diam and 102% area

4 inch O D has 11.76 up 60% diam and 166% area.

i run two 3 inch downpipes from my twin TO4s and have 12.94 sq inches area. i have 17 psi of backpressure at one bar boost. my downpipes run into a Burns Stainless Y and into a Borla 3 inch straight thru muffler and Racing Beat single.

given the 4.41 inch area of the 2.5 part to your exhaust i would focus on removing that first as Sean suggests.

as to egts...

they are extremely important as to tuning. ideally you need to log them digitally. you need them to be preturbo and for both rotors. it has been conventional wisdom that post turbos egts are approx 200 degrees cooler. i did a check this year and found 340 degree difference at one bar. i also found an extremely non linear relationship at anything but full throttle. based on that i have decided to continue to monitor my egts preturbo. you will also find that the front and rear run different temps and you can tune them equal using lag settings. AEM makes a voltage translator box w 4 channels and buy the thermocouples from Teamrip.com. they are FAST.

howard coleman

 

good info here, but how do you safley monitor EGTs pre-turbo, without risking the the life of the turbo... arent you risking a sensor going through the turbine wheel?

 

thanks howard for the great post it really helps out alot however I've got two questions.

1. 2.5 duals instead of 3" single should flow more correct? Not trying to stay with my 2.5" exhaust but just wondering if I should stay away from 3" single if the 2.5" duals flow more.

2. i've got a microtech lt8 that doesn't log egts so what would be the best way to log it? I have a zietronix that I was planning on logging one probe with but it won't do two probes. One would still be better then nothing correct? Also if i where to only use one and data log that one would you still suggest before the turbo? Somewhere like the turbine housing? also same question as r1xliquid!

edit: also does the lt8 have the lag settings that can change?

 

I know that your exhaust gases are spinning and that a large single tip promotes the formation of a vortex, whereas duals disturb the creation of such.

 

i don't see my Teamrip themocouples posing a threat to my turbine wheel. so far 8800 miles and everything is fine.

i do see not knowing your preturbo egts as a significant threat to your engine.

one egt is lots better than zero egts.

generally the rear rotor runs around 100 plus degrees hotter. you can get them very close to even by adjusting injector lag w a Power FC. i have no knowledge as to any other systems. ideally your egt bung should be approx 1.5 inches from the engine.

i am not familiar w the "dual" setup but as you can see from the above numbers it would offer more cross sectional area.

howard coleman

 

Don't try this with duals (lol): https://www.rx7club.com/rx-7-audio-visual-lounge-143/

 

I have dual egt probes tapped into the manifold before the turbo but a fitting welded to just expose the end of the sensor so the heat does not destroy it...I see my egt temps within 50-100 degree's F of each other. and have the Xcessive Lower intake manifold, so it seems to be doing the job nicely and no need to adjust injector trims from front to rear rotor housing. The less back pressure the better for rotary engines, get as much exhaust and heat out as possible. I run a 1.15 A/R housing and my dp steps up from a 3" vband right out of the turbo and immediately steps up to a 4" diameter and then to the 3.75" exhaust. Anyway, do what you want, but if you want the 500 whp plus range at high boost levels, do it right and get a 4" dp and big exhaust.

 

Exactly.

 

I did 3" all the way back with mandrel bends and a 3" thermal R&D muffler.

so far I'm pretty happy, it's nice and quiet.

 

This is shaping up into a good thread.

Re: the 4" full exhausts, how streetable are they really? Even with a muffler in the midsection, I would imagine the drone would be annoying and even the part throttle would be crazy loud, no? I have looked into running the HKS Ti 4" mid and back section and have heard it's loud as all hell.

 

It is loud, but not as loud as you would think for being that large and no cat...at least the setup me and ernieT are running. Yes, it does drone and you have to crank your music up to hear it, lol, so its not quiet by any means.

 

I believe on a turbo charged engine, once you have a well tuned manifold, you can go as big as you can possibly fit (downpipe + exaust). I have the HKS racing titanium exaust and plan on getting a 4" downpipe made.

 

Doh! I meant to post a link to the discussion of the home made jet engine...
https://www.rx7club.com/rx-7-audio-visual-lounge-143/home-made-jet-engine-572834/
Interesting observation in that that discussion about correllation of diameter to EGTs.

The point I was trying to make though, is that you could not build an effective jet engine with duals, because spinning gases would be disturbed like they ran into a 90 deg. turn. God crys every time someone stops spinning exhaust gases.

 

Groundzero LIM guy here too. BTW, I also run a 3.5" straight through mp into a n1 dual tip. Its not to bad with the silencers in....but uncorked, its freakin' loud! I don't daily drive the car, so i don't mind. CJ

 

Yes it actually is 5" all they way back from entry to exit

-S-

 

I saw a 2" downpipe on a T66 12a last week, I about died.

 

my buddy has a civic with a 2 1/4" downpipe with gross crush bends (like, really really badly bent crush bends) that makes 410whp on pumpgas... I'm sure it's FAR from being optimal for performance but it does seem to work!

 

3.5 all the way...

 

i think I may go with just a cork sport 3" cat back and then something like a 3 or 4" downpipe.

 

I built a 4 inch all the way back for my FC and then realized I could fit a 5 inch setup no problem even with the convertible cross member being so big. Plus building your own setup is so much cooler.

I have several pics of my setup on this forum somewhere. I did how ever ruin a good digital camera taking pictures of the welds so all the pics look like they were under water.