arghx

iTrader: (3)

Way back in December 2005 I put down 172 to the wheels on my series 4 GTU. The car is dead now due to a recent accident at an intersection.

Relevant mods at the time were, to the best of my recollection:

--s4 keg, manifolds, and electronics

--street port on the intake side. exhaust side had the T2 sleeves (which don't have the baffle) and I believe the ports were matched to the sleeves. I didn't build this motor.

--pineapple auxiliary port sleeves. 6 port system didn't work most of the time, so they were wired open. the electric airpump method I tried later was not reliable.

--RB collected header, test pipe, RB 2.5" catback

--SAFC for fuel control

--crank angle sensor advanced a few degrees. remember this was before the Rtek 2.1 was available


If I could go back and do it all again, here's what I would do:

--put a presilencer in the exhaust instead of just running a test pipe. The exhaust porting and T2 sleeves make the sound pretty harsh, even with the RB catback

--get an Rtek 2.1 for sure and ditch the SAFC while adjusting the CAS back to where it should be

--put the factory smog pump on

-- if I weren't cheap/lazy, convert to s5 manifolds and use an Rtek and an rpm switch to control VDI and aux ports with the factory smog pump. I'd just use OEM solenoids to control them.

-- if I were lazy, I'd keep the s4 manifolds and use the Rtek to control an OEM solenoid for the s4 6 port system only

-- put a stock flywheel and clutch disc back on. it's not worth the pain in the ***. maybe I would have a stiffer pressure plate.

SoloII///M

iTrader: (13)

Thanks for posting this. I'll be taking my car in for some dyno time next weekend.

Spirit-RE

iTrader: (25)

I remember going through all the info you posted about this setup back in the day. Surprised to hear your airpump setup wasn't reliable.


Do you have any 1/4 times?

Black Knight RX7 FC3S

iTrader: (7)

so you had a lighten flywheel? Drivability is bad on the street?

172hp is pretty awesome, about same as a stock S5 TII lol

arghx

iTrader: (3)

After trying some stuff I settled on a Lincoln Mark VIII air ride pump. It drew a lot of current and fried a couple relays. I had to mount the pump and that took up space. I had that rpm switch in there and everything... I just never got it to work right for a sustained period of time. I was always fiddling with it. What's the frickin point when the engine has a factory airpump. Yes the airpump does put a little bit of drag on the engine (it's not clutched like the FD airpump). But then I wouldn't have had to buy a dual alternator pulley. I'm sure I could have made the electric setup work, but looking back on it I just don't see the point. Mazda never used an electric airpump for the aux ports. S3 and S4 used backpressure, s5 used the factory smog pump, and the Rx-8 uses electric motors.

If I could go back and do it again, here's how it would be:



You see, the OEM s4 relief solenoid is just a regular old 3 way solenoid valve. Pneumatically it works just like an s5 aux port solenoid, an FD turbo control vacuum solenoid, or a 3 port boost control solenoid (Greddy Profec etc) connected to the top port of an external wastegate. With the solenoid at rest, the aux ports are vented to atmosphere through the filter. With the solenoid energized, the aux ports are connected to the pressurized air from the factory pump. This is the same design as the S5.

I'd just use an rpm based trigger from an Rtek 2.1 to engage the solenoid, partly because I like my ECU to control everything. Pressure would then be supplied to the ports at whatever RPM I set in the Rtek. The whole system would use OEM hardware really. The only question is whether to keep the ACV on there and try to tap airpump pressure off of it or just hook up some brass fittings directly to the airpump itself.

My diff exploded when I attempted a 1/4 mile run and was in no mood to go back after it was fixed. Best time the car has is 9.7 @ 71 in the 1/8 mile. I guess that's not so bad back in 2004. It was probably a high 14 second car. It was completely full weight. There was no real weight reduction (A/C and power steering still there, but 88 GTU had most of the base model options) except ditching the factory exhaust.

Driveability is such a subjective thing. I had a puck clutch and a light flywheel. The puck clutch helped the car launch but it is needless to say abusive for the n/a drivetrain. I started to get more and more annoyed with the whole clutch and flywheel setup over time. It just creeps up on you like that. I ditched the puck clutch but I should have also gone back to a stock flywheel. These engines have no torque from a dead stop, even the turbo ones, so the lightweight flywheel is just irritating. I have a puck clutch and light flywheel on my T2 now. I wish I had gone with the stock flywheel and puck clutch. I'm only using the puck clutch because I need something that can hold 350+ lb/ft of torque and I don't want the super heavy pressure plates because they are known for breaking stuff on the FC clutch system.

j9fd3s

iTrader: (3)

it is! i think the RB steel flywheel is about what they should have off the showroom floor.

i think a stock 87-88 t2 flywheel makes the car almost undriveable, it certainly sucks all the response out of the car....

puck clutches do suck though.... no 2 ways about that!

i also hear you on the stiff pressure plate thing, i don't mind a small increase in effort, but yeah i don't need to break stuff

have you driven a good OS giken? or equivalent? a twin disc that isn't totally worn out acts like a stock clutch. its kind of amazing

arghx

iTrader: (3)

I'm not baller enough for a twin disc and I've never driven one on a rotary. I bet I'd love having one though.

j9fd3s

iTrader: (3)

ive driven a few, and rebuilt/good condition its great. the beat up one was like a light switch...