I use a long 1/4" carbide burr and stay clear of the plug boss as best I can.

I use the bottom of the Mazda end mill cuts as my max depth (for turbo pressures).

 

I just kind op copied the FD and RX8 end mill cuts on this RX4 housing. I did not touch the wall thickness of the boss itself on purpose (i reduced it slightly as I went a bit too deep with the end mill when removing the casting around the bolt boss below the leading plug boss) but I do not think it is critical. I also removed the the fin at the trailing boss as this is also done (altough its cast in and not milled) on rx8 housings. I also copied the end mill cuts found on the FD leading to the trailing boss as you can see.

Lets see what it does. I think it will work just fine =). at 70°C thermostat would be really nice. do you know if this exists for S4 water pump houing?

 

almost ready to rumble

 

graph of engine with MFR housings, these are flywheel numbers. I think actually we should have had a bit more peak torque. Top end after 9k the float level was too low. got some grose jet now so that should be fixed =)

 

New housings dynoed about same power as the MFR. Seems there really is a problem somewhere restricting peak ower. torque was around 250 Nm. when the mid range was leaner.

Here some footage.

Less is more, atomisation is really nice with these venturis. but the transistion is really tricky to get right. at we run F4 emuslsion, 80 idle, 120 air and 240 main. goes really well on top end but below 6k its too rich. :
For comparison normal IDA venturi, here we have no grose jet and you can see at the end of the run the float is about empty.

Dyno overview

Qualifying, just before the end one can hear the overly rich condition when coming out of the corner.

 

how high are you spinning it?

 

9k on track, power falls of anyway way to0 soon.

 

Some people are so kind to make really nice footage!

 

Boy that thing is really running well.
Is that your dad driving it?
Barry

 

In a quest for more top end, I opened up the exh a bit sooner and installed TII exhaust sleeves instead of the tiny RX4 ones, had to increase the size of the hole from 58 to 65mm. I hit some water in one housing but welded it again, hopefully it holds.

Also Barry, the modifications to the water jacked proved not to help anything. lifting is still there. I must say altough on the last race we had a problem with the fuel pressure regulator casuing the carb to overflow. therefore we drove on just one pump instead of 2 causing the engine to run quite lean up top, which could also cause to high temp around leading spark plug..

There was also sign of rear rotor hitting the rotor housing just slightly. not damage but one can see the carbon missing from the rotor where it hit

 

This is your original.



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This is what you have now.


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It may be wishful thinking but I think I see some improvement.

I think your specs are... stock water pump housing and pump. Are you running a thermostat?

How much water pressure are you seeing at the rear of the engine?

Have you seen the new RX8 impeller/pump?

 

Running TII water pump (cast impeller without gasket to recude clearance) at 56% of engine speed. no thermostat, denaturilzed water, water temps never exceed 80°C. did not measure pressure yet, but its on my backet list.


The TII pump look most like the Mazmart RX8 pump impeller wise. (3rd one in your pic)
it looks indeed a bit better now but its still a bit there

 

You are close to eliminating the temp problem around the plugs.

I would suggest that if you don't run a thermostat at least run the frame as a restrictor.

It allows the pressure in the block to go to about 45 PSI ...... raising the boiling point to about 300 degrees fahrenheit..



This is what a Boyesen design water pump impeller looks like...

I wonder who designed the new Mazda pump?

 

Hi Barry, do you have maybe a performance curve of a TII or mazmart pump? I am curious to know the tradeoff in flow when you increase pressure. at I am seeing almost no pressure increase over static pressure at the temp sender location. nonetheless with the bigger exh port the engine performes much better. got now over 260 Nm of torque and 306hp at the flywheel. it has still a bit more inside but we had no more time at the dyno. midrange was too rich and top end too lean. might need to use different emulsion tubes.

 

No I don't have the performance curves. I do have a generic chart that my mazmart seems to follow closely.... using aftermarket pulleys to slow the pump I get cavitation at about 6500 rpm (if I remember right).

You should be seeing over 40 psi at the back of the engine.

 

Finally got the dyno printout.

its going slightly lean at top end, which you can see in the curve.

 

Still going strong. for 2016 season we remade front suspension and subframe rack and pinion steering. the engine is now unopened for 2 seasons, approx 30 hours or racing and compression is still better than we measured after the engine was freshly together. the NRS seals are doing a superb job. I think it really proves for racing these engines are ultra reliable once jetted and balanced properly with good dry sump oiling system, even after a handful of 10k+ rpm misshifts per race. the only wears parts we changed where one set of Bosch W2CS plugs. thats it.

thats sub 50 dollar of parts for 30 hours of racing. now compare this to a 300hp cosworth BDx

 

You should enlarge the float bowl and use f2 em tubes and try some B9egv spark plugs. I make a separate float bowl that joins to carby using the float drain plug .I will do a drawing of the setup if you like .

 

I have extended bowl, but on that run the fuel pressure/grose jet was the issue. we now run 2 seasons with 3.4mm glass ball and 250 mbar fuel pressure without issues. I adjust main jet / air corr to balance the rotors so the end up with similar egt at the end of long straights.

 

Here some footage from the most recent race.


Car goes very well, reliable as a watch. the only thing that seems to wear in the engine are the side plates and side seals. rotor housing stay new with ceramic seals .D

 

Rubin,
I have had side plate wear that I attributed to tight side clearance …. less than .003".

You might try zero clearance corner seals.




Zero Clearance Side seals
Barry

 

Rubin, also I want to PM you another idea for your raised sparkplug area on the housings but I cannot add a picture.
So here is the picture.

 

What is the brake set up on that RX3? I have an old race car that needs to ditch the stock set up because you can't get new rotors anymore.

 

 

Here some footage from the last race, it was in Holland on Zandvoort track. No muffler on. Car went really well.