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IC will be welded up to have its pipes up the top... sometime soon.
Front Xmember will be back on after I finish tunning. Lack of it makes access to IWG arm easier.
Nope, 3.5" exactly. Feeds with same ID into oem MAF housing with a mesh in between, then reduces down to 3" till turbo intake. This setup never gave me tuning issues, though I hope not to have to rescale the MAF higher than 360g/s.
Sadly turbo outlet is only 2" and does 2 90deg bends at 2". Space wise, it couldn't be any better. After these bends it goes to full 3" till the throttle body.
Here's a thick aluminium plate my fabricator though of using to install IAT and pre-throttle body boost pressure sensor. The IAT one is actually taken from an OEM MAF sensor butchered up to take the NTC element and place it in a 1/8NPT holder of the sorts. I've actually broken 2 sensors to make one - but damn it works wonders as I get to keep the OEM calibration and not wonder if it is accurate across the board.
NTC calibration is nightmare material despite me having access to all the info required - pull up resistor value and position inside the OEM ecu, pull up voltage and the voltage vs temp. scaling inside the tune. Keeping the stock IAT sensor but placing it right was, I guess, the best way to maintain absolute accuracy.
Don't worry, I'll swap around the position of these 2 sensors so that the IAT faces all the airflow and the pressure one gets behind it. Probably matters not - but why not do it right.
I'd have a question for those of you with more tuning experience than my years of owning a drivers licence... is the rear O2 sensor actually used in anything but emmissions ? Whenever I reflash the tune I lose all trims(obviously) but the car won't catch an idle when coasting or pulling up to a stop. After it stalls a few times it will start to get better and eventually it will idle and drive perfectly with fuel trims + - 2%.
When tuning I set my idle to 2000 and it would idle at about 1500, when I'm done I set it back to 1000 not to have it stall 40 times a day.
This only seems to happen to my RX8s that have their rear O2 broken or not connected. In my case the harness is messed up and would take 2 hours of faffing to replace the rear o2 sensor connector. Wondering if that's a job for a rainy day or my issue is somewhere else. Issue was present ever since - not related to this IC/exhaust revamp.
Last edited by ciprianrx8; 01-19-2023 at 01:50 PM.
I'm surprised that maf setup doesn't give you tuning problems ...looks too close to the bend to me . Plus the stock maf housing tends to fall to bits when cut up like that.
You should get something like this complete with a honeycomb straightener IMO : https://performancemrp.com/i-3049764...tegory:1389196
For IAT I use a fast GM sensor ...sure I had to scale it but that wasn't a biggie .... Just matched it to the Mazda ambient temp sensor on a hot and cold day and extrapolated in between.
I'd have a question for those of you with more tuning experience than my years of owning a drivers licence... is the rear O2 sensor actually used in anything but emmissions ? Whenever I reflash the tune I lose all trims(obviously) but the car won't catch an idle when coasting or pulling up to a stop. After it stalls a few times it will start to get better and eventually it will idle and drive perfectly with fuel trims + - 2%.
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Nope ...rear 02 is just there for checking cat .... I run all my 8s without it and have zero issues like that.
A few things can cause those issues one being the maf setup (see my post above). Another is a dirty throttle.
Nope ...rear 02 is just there for checking cat .... I run all my 8s without it and have zero issues like that.
A few things can cause those issues one being the maf setup (see my post above). Another is a dirty throttle.
Strange. If it had been only this car, then yes I'd start tearing the intake. But given that it will self heal within 5-10 mins of driving and be perfect at all times, temps, loads, etc till the next reflash...
A bone stock rx8 I once had but w/o rear o2 did exactly the same. That one seemed to restart combustion too late while rpms were dropping in decel and thus stalled for a while before it caught on that it has to do its thing sooner. This one fluctuates timing from -15 to +20 while idle hunting.
Perhaps the ECU learns a relationship between commanded throttle body opening vs actual realised opening and mine is just way off. Might look into the thr body snagging, I've got a spare I can try.
if the rear O2 is present it will correct the tables as if the cat was there. if it is disconnected (and ecu doesn't receive false inputs) than ECU ignores it.
as for the pipes of intake / exhaust..
if your exhaust is 3" and doesn't cause back pressure. And you have much higher (by magnitude higher) volume flow since the temp is higher and pressure is lower than the intake ( the well known PV=mRT where mR is constant) you don't need same piping size on the intake (post turbo).
Remember each transition (bend or change in cross section) is energy loss, also cross section can induce resonant frequencies that could get coupled with intake resonances and create either constructive or destructive interference.
Only thing you get with big intake pipes is lag and not in relation to turbo lag since its low boost, but MAF reading and Engine Load.
Last edited by MilosB; 01-20-2023 at 12:45 AM.
Reason: added content
There's more to big pipes than just lagging turbo response. Of course no one wants lag and automakers even moved intercoolers inside the intake plenum to reduce that. But there's a merit to large diameter pipes:
630 cfm = ~ 357g/s = ~ 47 lb/min of airflow.
Yellow line is where I started, blue is where I ended up. The target value at the bottom is indicated by Garret and I'd say they do know their stuff a lot better than I'd claim to. My expertise is something else entirely.
Since I was changing the IC to something bigger to aid with same flow but at lower pressures, I'd figure now is the time to improve on the pipes as well.
Last edited by ciprianrx8; 01-20-2023 at 07:54 AM.
Strange. If it had been only this car, then yes I'd start tearing the intake. But given that it will self heal within 5-10 mins of driving and be perfect at all times, temps, loads, etc till the next reflash...
A bone stock rx8 I once had but w/o rear o2 did exactly the same. That one seemed to restart combustion too late while rpms were dropping in decel and thus stalled for a while before it caught on that it has to do its thing sooner. This one fluctuates timing from -15 to +20 while idle hunting.
Perhaps the ECU learns a relationship between commanded throttle body opening vs actual realised opening and mine is just way off. Might look into the thr body snagging, I've got a spare I can try.
I have definitely had instances where an 8 wont hold idle after a reflash like you are seeing ................ that's how I know for a fact that the better/and closer to stock that your maf setup is the lower the chance there is of this happening. It's why, if someone wanted me to tune their setup with the maf like you have it ...i'd refuse to do it till they fixed it !
Don't know about emmissions anywhere else, but in Europe they are as tight as they get. Hence my suspicions about this rear O2 sensor being used more than what it's commonly known for. While digging around I also found this:
As I've said this idle hunting also happened on a similar EUDM ECU with a 100% stock intake and everything(but no rear O2 plugged in). Maf numbers didn't change by more than 1 g/s during idling on both cars, that's why I don't doubt the current setup. Since the rear o2 sensor outputs a plain voltage, perhaps it would help shorting out those sensing wires to tell the ECU for sure that the rear o2 sensor is buggered and not to be used at all. ATM 2-3 meters of free ended wires may or may not pick up stray voltages.
So this IC/exhaust revamp is now done from a mech. standpoint. Generally pleased with how it turned up, once I free up some time to tune it we'll see if the trouble was worth it.
Before IC/before
After Not expecting any cooling issues. About 1/3 of the front grille is open for fresh air to reach the AC and coolant radiators. Compared to old setup, this intercooler actually allows for more air by its right/left sides. This aero front lip also helps with enlarging the front air grille.
I was told(and it really was, lol) the crashbar was reinforced on the back to account for minute trimming of its U shaped profile. Well, pray to whoever floats your boat that I don't get to use it.
A bit worried that the top 3-4 rows of the IC are covered entirely and thus do no cooling at all, but then again this IC is twice as thick as the old one, and has the same area exposed to moving airflow. I figured it's not worth cutting the core up just to eliminate those 3-4 rows. On a street car it shouldn't be a problem.
Granny-drove it for a bit and didn't build any fuel trims past 3%. The exhaust resonator I have selected does wonders and can say the car is quieter than my stock RX8. Major win here. Major loss during city driving because it sounds like the beginning of an earthquake when pulling off, but dead quiet past 2000 rpm. Need a free weekend with nice weather to revamp the tune too. Basic change = returned to wastegate spring pressure all the time and hoping to move to a softer spring.
Last edited by ciprianrx8; 01-21-2023 at 01:52 PM.
There's more to big pipes than just lagging turbo response. Of course no one wants lag and automakers even moved intercoolers inside the intake plenum to reduce that. But there's a merit to large diameter pipes:
630 cfm = ~ 357g/s = ~ 47 lb/min of airflow.
..... indicated by Garret and I'd say they do know their stuff a lot better than I'd claim to. .....
your start position of 2.25" acc to my calc (assuming 1.6PR, the higher will give slower speed) gives 252kmh
don't you think all the car manufacturers also follow garrets recommendations and install piping (where I have yet to see a sub 400hp car with more than 60mm id intake tubing)?
Also you can argue that the max flow number is at peak power RPM, which is good point to optimize if you are shooting for the max peak power, and not max overall power.
I gave you the simple comparison. A 3" exhaust will flow by volume much much higher rate (8+ time higher volume flow) with almost no backpressure. Yet you think the difference in intake manifold and turbo pressure was lost due to the 2.25" and that the 3" will help. by that analogy you would need at least 4" exhaust.
at exhaust pressure at same ratio as the intake (unrealistic back pressure after turbine), it will flow EGT/IAT times higher volume (plus the fuel)..
other than that, a much better setup no questions !
Weather update - winter seems to be gone for the year and I remembered I had this thing parked for a while. It needs a tune (again, for the 435th time). At about the 356th time I got fed up with recording my gauge screen with a camera pasted on the windscreen... and thought there has to be a better way around this.
So I leveled up my layman's skills in anything OBD2 related and came up with this:
Before now I was watching video recordings and adding data by hand to existing logs. No longer needed - I finally figured out how to have all my gauges in one log - MazdaEdit's log. And I'd be dammed if I bought another logger or another piece of hardware to have wires dangling about the cabin.
One interesting hurdle that took me some time to figure out was this:
It kind of worked, it kind of didn't. Those nasty spikes would also show up on every other parameter - and every other parameter would work too. It turned out that 2 people talking over each other is no good way of doing anything so one of them had to stand down and be reduced to a listener 90% of the time, answering only 10% of the time. The other would do all the asking. Lots of corner cases here, but with my usual stubbornness I've patched them all.
I can't wait to do some logs with this new setup. Things will get spicy - can't wait to see boost vs emap vs wastegate duty cycle vs rpm vs load vs maf.
Some great progress ! That's gunna be a real boon for boosted setups!
Also : Hope you have some 100+ octane fuel in it when you are boosting that high!
Those graphs were me twisting a potentiometer on my desk. There's no time to test every future straight on the car, not when those features are mission critical. I haven't yet pushed a pound of boost with this new-ish setup. Life happened, my daily 8 needed a fix that turned into a 2 day ordeal etc. I had to read my tuning notes again as I've started losing my edge on what table does what and why I did some things I did here and there. And now I see that the latest ME update wiped off all my custom defined maps. #yay
Can't tune without my + - keys...
Last edited by ciprianrx8; 03-02-2023 at 03:20 PM.
I had some time to churn on this thing. Ofc the battery had to go flat and find I've been too lazy to finish up the vac. hose routing and all. To my mind the car was ready to rip.
There are good news, and bad news.
The bad news is that I can no longer control boost at all and I can't use my BOV to have it bleed boost(as a failsafe) to the point it runs NA. Even with the BOV set to open up, there's simply not enough flow recirculated through it to prevent boost buildup. Flooring it with the BOV open still does 5-6 psi.
The good news is that this IC and exhaust revamp seems to be doing something, as I can no longer control boost using the same wastegate spring that used to require NO boost being fed to it, in order to keep 12psi till redline. I need to move down to a softer spring. I can't floor it like this, as boost jumps up way over my limits. I'm also very proud of my logging setup, so I'm dropping a low effort logging run to give you all a taste.
Anyway:
I can't really compare stuff here, but it seems that I've dropped about 5 psi of emap by 6000 rpm. That's not a lot, but still, a bit better. I hope that by reducing EMAP and boost while keeping a decent power level is possible. At the moment I am very pleased that the new exhaust is even quieter than the stock one!
The car now runs, but poorly as I like to start pig-rich to the point of rich misfires then work my way up till the butt-dyno says there's no improvement in going any leaner.
Will be back....
Last edited by ciprianrx8; 03-11-2023 at 07:29 AM.
Removing one drop out of the emap ocean matters not. With that much disparity it’s just a matter of time before the perfect storm arises and sinks your boat.
Fixing that should be your #1 priority over anything else. Because you can’t tune away a blown engine, you can only spend a small fortune rebuilding it …
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01-13-2023, 10:13 AM
. Plus the stock maf housing tends to fall to bits when cut up like that.
