When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
The intake air leak was causing the car to run rich under part throttle where UIM was still in vacuum but turbo was providing slightly positive pre-TB pressure. This indicated the leak was a pre-TB boost leak, rather than a manifold/vac leak (where the car would have run lean under vacuum at part throttle). Once I knew where to look I found and fixed the leak in a few minutes. Car is running like a champ again. Amazing how much nicer the car drives at an AFR of low 11s rather than low 10s.
While fixing the boost leak above I installed the new oval shaped K&N filter to replace the old one that had clearance issues. Same location as previous filter - behind front bumper with flange pointing directly back into engine bay.
Installed a filter wrap on the new filter to keep water out of the MAF tube. This should resolved the issue I previously had running boost in the rain, where moisture was sucked past the old filter into the MAF tube, interfering with the MAF sensor signal.
Thanks for the link. I've read it before but completely forgot about it. Let's continue this EBC discussion on that thread. I'm now convinced to test pre-TB vs. post-TB EBC signal source, regardless of what I think the result will be I'll do the test in another week as I've got a few things I need to address first.
Did some testing. Pre-TB signal source does not work with my brand of EBC. Best signal source for EBC with my setup is still post-TB per my diagram earlier in this thread. I've added a write up here: https://www.rx8club.com/series-i-maj...0/#post4717464
Last edited by JimmyBlack; 09-16-2015 at 10:07 PM.
Good write up man.
RE: EBC Input, I had the same thing as you with my GFB G-Force II, I've tried all sorts of different configurations and ended up leaving it post-TB.
Can't wait for the day all us Turbo Kiwis are together in one place
Ross
It's a well known best practise to run a turbo rx8 with no cat. Here's my experience of before and after cat removal.
About a month back I decided to knocked out the high flow cat from the BHR midpipe. It smelled like it was doing nothing, and BHR clearly state it's not suited to turbo applications.
The net result was an immediate gain of 4psi of boost. I wound down the wastegate actuator and re-adjusted the EBC to bring the boost back down to the same level as before the cat removal - 11psi across the rpm range. I wasn't able to get any logs of before and after, so I've only got feedback from my driving experience. Comparing 11psi before cat removal vs. 11psi after cat removal, the car is performing noticeably faster across the rpm range, with improved throttle response, particularly at low rpms.
Removing the cat increased the pressure differential on either side of the turbine wheel, allowing exhaust gas to flow through faster, applying more force to drive the turbine shaft faster/harder resulting in more boost from a faster spinning compressor wheel.
The removed cat also means that the backpressure seen by the engine's exhaust ports has been significantly reduced as less backpressure required to spin the turbine wheel to the required boost level. How does this result in better performance? My guess is that the reduced backpressure means more exhaust gas is expelled from the chamber during the exhaust cycle, allowing more fresh air/fuel in on the intake cycle. Less chance of detonation from hot exhaust gases that remain in the chamber during compression cycle and more power from more air/fuel. In theory reducing the backpressure should allow us to run more boost safely - to a certain degree.
I'd love to know what the backpressure my exhaust manifold was running before and after removing the cat. I haven't seen any turbo rx8s doing this to date and yet this is one of the factors that determines how close to the edge you can run a turbo setup. Maybe it doesn't matter as much on a Renesis as intake/exhaust cycles don't overlap.
...and is my setup with a small T25 housing and low flowing compressor wheel seeing the same backpressure (and/or exhaust pressure ratio) as Brettus' T3 housing running a 400whp setup, and therefore equally likely to pop my engine?
Hmm, I was looking at the specs for my Greddy SE exhaust the other day, I absolutely love the sound of this exhaust but I'm pretty sure it is only 2.5". I've been wondering myself on how much better my EBC would be able to hold my 9psi peak if I was to upgrade to a full 3"...... However, I'm not surprised in the difference you saw by gutting the cat.
Currently running 3" catless BHR, choking down to Greddy SE which I believe is 2.5".
Last edited by RotaryMachineRx; 10-07-2015 at 09:34 PM.
I installed a new 3" exhaust to replace the OEM one recently. I'll post details later but here's a rough graph of the observed boost change from the exhaust change. This is using wastegate only - no EBC settings.
As expected, gains were in the upper rpm range. Peak boost has moved further up the rpm range, and there was a 2psi boost gain. No noticeable changes below about 5krpm.
Total boost increase from cat delete and exhaust swap was 6psi. Makes me think the car was running some very high/unhealthy back pressure previously. Not good!
I had a new exhaust made up recently. After living with it for a few weeks it's time to post up the details and impressions. I'm going to work through the decision process for the exhaust specs so others looking to do the same can see my reasoning (right or wrong) for doing it this way.
Goals:
Improved performance
Not too loud/droning while cruising (this is a daily driver)
Exhaust setup is Greddy exhaust manifold, T25 turbine housing with internal WG, Greddy downpipe, BHR midpipe with standard BHR resonator and gutted cat, OEM catback.
The new exhaust replaced the OEM 2.25" catback.
First up I had to decide on the main catback pipe size. The common sizes that fit resonators and mufflers are 2.5", 3" and 3.5". I ruled out 2.5" as I'm paying good money to get an exhaust that improves performance and 2.5" is just a touch too restrictive for the my 300+whp power target (work in progress). 3.5" would be ideal for performance but I ruled it out due to excessive noise and ground clearance issues. 3" is ideal. If I were doing this for an non-turbo setup I'd probably go with 2.5" for the street, though for NA it'd be all about the sound, not the performance gain.
It's hard work using a daily driver with an exhaust that drones when you're cruising. To avoid this I went with a Y split from the 3" pipe into two 2.5" pipes to dual mufflers. I felt that the dual muffler setup offers better flow than the single entry dual exit mufflers due to fewer pipe bends. Using dual mufflers also allowed me to use smaller pipe diameter to each muffler to decrease noise without reducing the exhaust flow.
Perforated rotary specific (high temp) mufflers were used.
Impressions
The exhaust tone at idle is much deeper than OEM, though not much louder. In hindsight I went overboard on keeping it quiet as it's only a touch louder than OEM through the whole rpm range. Next time I'd have the same setup but replace the mufflers with resonators. Drum-beats, you need to post up your exhaust setup!
Pros
Approx 10-15whp more power at same boost level as before (10.5psi)
No ground clearance issues
Nicer sound
Backfires when coming off boost around 5krpm and during power changes at high rpm, kabooom!
Cons
It's just a bit too quiet - No big deal here, if/when I go to an external wastegate I'll use a dump pipe with resonator to make it bark when I put the foot down.
Last edited by JimmyBlack; 10-18-2015 at 06:30 PM.
Reason: resized pics
As requested, my exhaust setup is as follows:
I have a custom Sinco manifold, this goes into a 2.5" up-pipe and through a top-mounted MasterPower MP-R545 turbo. From there it goes into a 3" down-pipe, through 2 Adrenaline-R Torque Resonators. It is then reduced to a 2.5" straight pipe, this goes into a y-pipe and then out twin 2.5" exhaust tips.
My exhaust has a maximum noise volume of 97dB, it has (in my opinion) a nice deep (deeper than a normal RX-8) tone. It does not drone at idle or cruise, and it backfires and shoots flames when driven hard.
Last edited by drum-beats; 10-19-2015 at 03:55 PM.
It's just a bit too quiet - No big deal here, if/when I go to an external wastegate I'll use a dump pipe with resonator to make it bark when I put the foot down.
Hey, you can't get off that easy, where's your build thread?
Sound clip coming...and some logs.
MAF is now reading 330g/sec with new exhaust - about 20g/sec improvement.
From other people's accounts I'm thinking that I've pushed my setup about as far as I can safely. I want to get a better picture of the limiting factors that stop us from pushing for better performance. To do this I'll be installing the following sensor feeds:
IAT sensor relocation to post-IC charge pipe to see whether the compressor is working outside it's useful efficiency island
Exhaust manifold pressure signal so I can check the exhaust/intake pressure ratio
I haven't seen any exhaust manifold backpressure figures for rx8 turbo setups to date, and I think visibility of this is one of several factors that would help people realise how far they can push their setup.
Hey, you can't get off that easy, where's your build thread?
I'm getting there.
Currently getting the car valued for my new insurance package.
Going to be a 'Road Legal Race Vehicle' haha. Should mean I get a better return if anything bad happens as it will be insured for what I have put into it, not 'market value'.
Once all that is sorted, I'll get around to a build thread.
What turbo manifold did you go with? I want to boost mine but can only find one turbo manifold offered and it's around $1400 but that seems a little steep.
What turbo manifold did you go with? I want to boost mine but can only find one turbo manifold offered and it's around $1400 but that seems a little steep.
First up I'm gonna say that it sounds like you haven't done enough reading yet, as you should recognise that my manifold is a very common Greddy one that comes with the Greddy kit pictured in my first post. If you wanna do this turbo thing, you'll save yourself a crap load of time and money by reading up some more before buying anything. But I'm not here to bust your *****, so I'll give you a push in the right direction.
For the money you're talking you should be able to pick up a whole Greddy kit from the for sale section of this site. A second hand Greddy kit will typically include other bits that you'll want to use such as intercooler, cold side piping, BOV and maybe the turbo which you'll probably want to rebuild, and probably change the compressor wheel to a higher trim (57-58 is about right for the Greddy turbo).
If I were to do it again (...say in 6 months from now) I'd fabricate my own well designed low mount manifold for better performance. By well designed I mean stainless steel, T3 flange, external waste gate (angled correctly off the centre runner or collector), suitable pipe size (see Brettus 111 thread), equal length front and rear runners, smooth bends and collector. You can read up on this stuff if you need to know more...or you could just build/buy one of these which is the ducks nuts.
First up I'm gonna say that it sounds like you haven't done enough reading yet, as you should recognise that my manifold is a very common Greddy one that comes with the Greddy kit pictured in my first post. If you wanna do this turbo thing, you'll save yourself a crap load of time and money by reading up some more before buying anything. But I'm not here to bust your *****, so I'll give you a push in the right direction.
For the money you're talking you should be able to pick up a whole Greddy kit from the for sale section of this site. A second hand Greddy kit will typically include other bits that you'll want to use such as intercooler, cold side piping, BOV and maybe the turbo which you'll probably want to rebuild, and probably change the compressor wheel to a higher trim (57-58 is about right for the Greddy turbo).
If I were to do it again (...say in 6 months from now) I'd fabricate my own well designed low mount manifold for better performance. By well designed I mean stainless steel, T3 flange, external waste gate (angled correctly off the centre runner or collector), suitable pipe size (see Brettus 111 thread), equal length front and rear runners, smooth bends and collector. You can read up on this stuff if you need to know more...or you could just build/buy one of these which is the ducks nuts.
Thanks for the push. I'm brand new into the rx8 world and just joined this forum yesterday. I put in a search for turbo manifolds but not much came up, that's why I asked. I appreciate the help, I really do.
In the quest for more boost with minimum risk I've replaced my previous mesh screen with a honeycomb air straightener in the front of the MAF sensor tube of the intake. This will provide very accurate MAF sensor readings, which in turn will contribute to more accurate AFRs.
Air straightener arrived yesterday, and went into the car last night. Was pre-cut to suit the pipe size and didn't require any trimming, just a bit of time and some firm hands to get it into the tube. Once the trial fit was complete, superglue was used around the edges of the mesh before pressing it back into place for the final time.
Driving to work this morning the car idled and pulled more smoothly, more like what a factory turbo rx8 might be like. I haven't driven it at WOT yet as AFRs are a little lean after changing the pre-MAF setup. The tune may require a bit of a tickle up.
In hindsight, this inexpensive part should have been on my "must do" list during the prep stage of the turbo build. For turbo cars this is strongly recommended, though a retune may be required after installing.
NA rx8s with AEM intakes would see improvements using this part also.
Out with the old (right), in with the new (left).
Minimal restriction to intake airflow.
Last edited by JimmyBlack; 11-17-2015 at 03:08 PM.
I installed one last year but honestly didn't notice any real difference as far as readings are concerned. The main reason I replaced the screen is because I've had issues with the screens getting dislodged and sucked in. That WILL cause erroneous readings
I installed one last year but honestly didn't notice any real difference as far as readings are concerned. The main reason I replaced the screen is because I've had issues with the screens getting dislodged and sucked in. That WILL cause erroneous readings
Never seen one that big ! The bees must be huge in your parts !
Never seen one that big ! The bees must be huge in your parts !
Everything is bigger up here... Wait, that's your side of the equator... Sometimes I think you are the only one that gets my humor So much for the eBay honeycomb but no procreating around here I really did only put this in because the screens were getting sucked in.
09-14-2015, 05:01 PM
I'll do the test in another week as I've got a few things I need to address first.
but no procreating around here I really did only put this in because the screens were getting sucked in.