Vacuum Readings S4 TII
 

A quick one, what is the optimum achievable vacuum reading at idle hot 750rpm S4 TII.

My car is reading from 18-19inch/hg at full warm idle 750rpm and has an idle AFR of about 12 even.

Pyro reads from 550*c to 750*c under light/medium loads.
No boosting yet as needs to be leaned out running way to rich under boost (9.5-10:1)

just from those few details, that is one healthy (stock-ported) motor. I have seen videos of FD's with brand new engines (not remanufactured, brand new from Mazda) pulling that kind of vacuum.

The stock idle afr is too high. Lean that to 13.5. Your boost afr's like you said is way to high. Just like mine that's funny, in the same exact region. Why is this? All I have is the rev t2 exhaust, fcd, and s5 turbo with s4 engine. I'm thinking this is the reason why mazda was known to richen our cars out far beyond belief. I always thought my car was the only one being so pig rich.

I think it's just normal...

Yeah its really quite strange you would think with all the mods done to my car i would be needing LESS fuel then the stock mapping?! I think by freeing up the intake and exhaust and adding in a more efficient late model hybrid turbo etc etc you actually increase the volumetric efficiency of the engine so that less fuel is needed in that band range to make good power. May I also say that this motor was NOT ported whatsoever, Unless flow benched while ported I only trust MAZDA's intake manifold intake engineering. I can turn up the boost and play with intake charge cooling mods before I will Port.

1987 RX-7 TII 94xxx km's
Rebuilt to OEM spec, OEM 2 pc seals, Hand fit OEM side seals, all new springs, seals and o'rings.
RB Rev TII Full exhaust
Greddy 720cc secondaries
Treperformance 255LPH pump (walbro rip off, Nice quality though)
Rtek 2.1 ECU w/palm
Innovate LM-2 wide band
Home brew TID
S5 TO4B V-trim Hybrid 360* thrust bearing Garrett rotating assembly .50a/r coldside housing
Synapse Synchronic BOV
K&N drop in oem filter
Crane cams HI-6 ignition box
Autometer ES boost and Pyrometer
Act Streetlight flywheel
Centerforce Clutch

I haven't tried tuning with the rtek quite yet, is it possible to tune using AFR gauge while driving?? I can't quite seem to get Rtek chip to log AFR input nicely yet quite an annoyance.


So is 18-19"Hg not too bad for a stock port motor? This was a core rebuilt at 92xxxKM and it had perfect housing and I used Hand fit side seals and FD corner seal springs OEM apex seals and springs, all new springs and o-rings. NO PORTING.

19 inches at idle is what bone stock civics pull (99 D17Y8 single cam vtec), I have measured. and they have about as mild of valve timing (porting equivalent) as you can get when vtec is not engaged.

What was your side seal clearance? how many thousandths of an inch or millimeters? I have been told that a tight (but properly fitting) side seal clearance helps compression a lot. I'd bet that thing is making at least 110psi compression (7.75 kg/cm^2 as the Mazda tester would use)

your AFR is richer because of the fuel pump coupled with the stock FPR. An FPR is like a wastegate; if it is undersized, it will not bypass enough, and pressure in the system will rise.

One of my junk rebuilds with worn parts pulled 14 inch/hg at a 780rpm idle. It was strong engine...your engine sounds like its in great shape.

Every engine that I have built for myself has had atleast 120psi compression+ The handfit side seals really make a HUGE difference on rebuild compresion especially coupled with new springs all round and the newer style oem apex seals. Not only that but really good compression eats up lots of other issues like hot start and cold start issues, the higher the compression makes it easier for the engine to deal with most dynamic running conditions (eg hot start etc).