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.
IC selection is more critical than you might think , and more so on our cars. I went through at least four iterations before getting it right . Have a read of the IC selection notes here :https://www.rx8club.com/series-i-maj...1/#post4959665 .
the same formula for calculating effective rotary engine WHP relative to piston engine WHP due to the cfm required per hp difference applies to the intercooler as well.
an IC rated for 700 hp is generally stated for piston engines
700 hp rating x 0.7 RE factor = 490 rotary hp rating
but you’re probably better off rounding that down to 450 whp to be conservative. The actual factor is slightly higher than 0.7, so that’s on the conservative side as well.
.
Changed my measuring setup to find out if I need a bigger IC. I had my doubts before but now I'm sure I need a bigger one. From the outlet of the compressor to the outlet of IC I get a 6 psi drop at ~300g/s. Deff. not acceptable and will be fixed ASAP.
Next time I take it for a spin I shall have a full 3" exhaust and a much larger IC. Should feel much better. Until then I got myself a splash screen to suit.
Last edited by ciprianrx8; 11-27-2022 at 08:40 AM.
First in the line of hw improvements is the intercooler.
New one is twice as thick and twice as tall, and won't have these 90 deg sharp bends the current setup has.
Hoping that by deleting these bends and enlarging the core I'll shave off the 6 psi I am currently losing. Hoping for less than 2 psi drop from turbo outlet to LIM.
Photo above tells... nothing. It will sit rotated 180deg on X axis and with straight out couplers, not 90 deg as is right now.
New IC will look like a proper U with no useless bends. I got the size just big enough to fit entirely upright. Here's to hoping it won't absolutely kill all airflow for AC and coolant radiators. Previous setup worked wonders in this direction.
Not sure if I shall take the opportunity and enlarge charge pipes diameter from 2.25" to 3" where possible. Depends on who would take up this job...
Last edited by ciprianrx8; 12-04-2022 at 10:46 AM.
When doing these upgrades remember that each thing potentially increases air flow ..... and increasing the air flow could potentially also increase knock. I'm not sure how you have managed to avoid a major detonation up to this point but you could potentially create one now even though you are improving the setup. Something to be aware of when testing for first time.
There's a saying in my native language... he who once burned his tongue with soup will now blow even on a spoon of yogurt to cool it off.
The 3 reasons why I haven't blown this thing up:
I have electronics in place that monitor anything that's possible and take action faster than I would ever notice; for example transients from decel to full boost may create lean pockets that are indetectable by manual monitoring... but not to a rock doing maths faster than the engine spins. Besides the hoard of protections, limiters and corrections I already run I'm also considering doing an EMAP limiter now. I may say that whatever I've designed poorly from a mech. standpoint is at least safeguarded electronically. Like putting 3 leashes on a pomeranian dog(but it's slowly turning into something bigger).
PV = NRT fallacies on my end... too many of them. By the time I'm done improving a tiny bit of everything there will be little left of the initial configuration I started with 2 years ago.
Having an overall viewpoint from side seal clearance to bits inside a processor helps suggest where issues may pop up and prevent them. Though having your boost cut off entirely and all of a sudden is not nice, it beats pulling an engine.
I'm not chasing more boost or more airflow here, I wanna get the absolute best torque that can be done with 10-11 psi of boost @ LIM and plain 100 octane gas. I've already toned down my EBC in anticipation of future hardware changes; of course I'll retune everything and start on spring pressure. Hopes up for having to put a softer wastegate spring too.
Last edited by ciprianrx8; 12-04-2022 at 02:04 PM.
Having gotten used to turbo life and recently thinking its still a slow car after all this effort and struggle... well winter arrived here where I live and I took out my winterbeater.
Well if I thought 12 psi was still slow, then a bone stock NA RX8 with the exception of a tune and decat is unbearably slow to the point it's just a boring slow car. Even more reason to make this turbo build even better, once you go boosted you can't go back. Like Paris syndrome... once you're done with 2nd gear there's nothing that engine can do anymore.
It probably feels even slower now that I've changed how the throttle pedal feels... because having the lower 1/2 of it do nothing leaves little control. This stems from the too large diameter thr. body where opening it 60% or 100 % makes 1% difference in torque. This worked wonders when there's a turbo making things exciting but it's kinda overkill for its torqueless variant. Will require getting some used to...
Before you ask, yes this map still opens the throttle body to 100% when you really floor it; there is no sudden jump in torque between 95% and 100% accelerator pedal position.
Last edited by ciprianrx8; 12-05-2022 at 02:51 PM.
I learned to value the lowest valley just as much as the highest mountain top but can appreciate wanting to avoid running back and forth between them. It will wear a person thin on every level, but I’m still feeling the desire for endeavoring to persevere.
.
Undoubtedly better than mine - but sometimes we make mistakes that we live with for the rest of the life of that thing.
It seems that 1) turbo flange bolts are imposible to work on with the engine in the car - so bad luck if the turbo needs replacing and 2) the brace beneath the clutch area will no longer fit... mine still does. If Mazda spent a dime to put it there, I guess they figured it was a dime well spent.
Last edited by ciprianrx8; 12-19-2022 at 09:52 AM.
Spent some good time chatting with this guy on Instagram. Good dude and seems to know his stuff. He has plans to really push this setup to the edge and IMO likely even a bit over the edge; it will be exciting to see.
Dropped the car off to have whole new 3" chargepipes(up from 2,25"), new intercooler x2 as thick and x2 as tall, plus 3" exhaust. Here's to hoping it won't take an EWG to bring emap down below 30psi at wot + redline + 10psi.
I guess that a good chunk of my EMAP is due to the turbo pushing air through less-than-optimal diameter pipes + lots of bends + a thin and long intercooler; having the turbo develop 3-4 psi less for same airflow may drop 6-7 of EMAP solely from this(in my setup).
Then there is the matter of the original 2,5" exhaust... but after my ****-poor experience with Racing Beat (Europe) I hardly have any expectations for it. Money down the drain, this exhaust. Should have taken my chances on building one from scratch and placing 3 intermediate mufflers on it.
Then there is the matter of the original 2,5" exhaust... but after my ****-poor experience with Racing Beat (Europe) I hardly have any expectations for it. Money down the drain, this exhaust. Should have taken my chances on building one from scratch and placing 3 intermediate mufflers on it.
replace the RB section connections to full 3" ones. or is there something else that made you unhappy ?
The flange that matches up to stock cat is indeed a p.o.s. and was planned to be chopped up and replaced with a 3" vband. Trouble is, I ended up with x10 the fab work I anticipated due to the very poor quality of the rest of the kit.
When doing these upgrades remember that each thing potentially increases air flow ..... and increasing the air flow could potentially also increase knock. I'm not sure how you have managed to avoid a major detonation up to this point but you could potentially create one now even though you are improving the setup. Something to be aware of when testing for first time.
I would keep the airflow (g/s) constant and free up the power and increase the reliability by removing obstructions.
With high EMAP he has more hot combustion gases remaining in the engine for next cycle -> he has to have higher density to cram in the same amount of air in to the remaining volume -> he has to have the turbo running at higher PR -> cooking the air and reducing the air density making the FMIC work much harder and he has this huge pressure drop in the intake also pushing the turbo to even higher PR -> increasing the probability of knock.
By reducing EMAP he will lower the remaining hot gases making ignition limited due to knock, less fresh air (% vise) in the chamber , the EMAP that he has logged is robbing him of very significant amount of power. I wouldn't be surprised that that EMAP equates to roughly 40-50hp....
A good turbo should not have EMAP vs IMAP higher than 1.5 ~ 2 for high PR apps for fast response, which this is not.
11-25-2022, 08:38 AM
but can appreciate wanting to avoid running back and forth between them. It will wear a person thin on every level, but I’m still feeling the desire for endeavoring to persevere. 
coupled with your own desire to bang on something