TWiR 1986 S3 TWR

[A7RXY]

Love the flames Dave ... also sounds good.
Dibs

[KiwiDave]

I've just put the mazda to bed and jumped in the Merc ... and it feels slow! I have this silly grin Loving my RX

[DKWW2000]

Great news Dave, bet the Merc seems quiet now
That would be a great Article in one of the Classic mags..............I read somewhere recently they were looking for similar type stories but cannot find it now

[KiwiDave]

Many issues sorted on the day. Interesting thing is that useable torque is available far higher into the rev range (because ... street port). Peak BHP @ 7600 rpm and peak torque (116Nm) @ 5500 rpm. And it's still useable at higher revs too. 6000rpm / 115.6 Nm 6500 / 114.5 7000 / 111.3

So the SU is a quantum leap over the Nikki but it's down to useable torque rather than horsepower. The dark arts of carburettors and why some work better than others is a discussion zone the size of an arena The point of the excercise was that I've driven both and the SU is certainly a vast improvement in performance. That's why the Shelsley Walsh Hillclimb was so important in demonstrating the difference in the two setups.

The whole overrun issue is an interesting one. It is not worn spindles. It's more down to how the carb is designed to work. This was pointed out by their carb guru. The throttle plate incorporates a device which introduces air on overrun. It's more an emissions thing but it works better with a reciprocating engine that provides more engine braking . A rotary engine as we know doesn't do engine braking nearly as well. The answer is a blank throttle plate of which there are precisely ... none available at present. So this is an anomaly rather than a fault and essentially means that there is less engine braking available and you adapt accordingly.

Merc is quieter and a lot more relaxing

[Hobbawobba]

Awesome as bro! Glad you finally got it all sorted man!

[spirit r]

OEM Nikki is making 167 Nm @ 4000 to 7000 Nm without any mods, so i am confused about your Numbers Dave.

BTW i am glad about your positive results for making your racetime better.

[KiwiDave]

Thanks Thomas. My mistake and sorry for your confusion. Torque figures are lb-ft not Nm and I seem to have lost the ability to edit my posts at any time.

116 lb-ft = 157 Nm

115.6 lb-ft = 156.7 Nm

114.5 lb-ft = 155.24 Nm

I'm not a huge fan of posting up figures because there are so many different sources to quote from. As far as I am aware and I've compared many sources, a S3 UK spec 12a (113 PS) produces peak torque (148 Nm / 109 lb-ft) @ 4000 rpm. This drops to 109.7 Nm / 80.9 lb-ft @ 6500 rpm.

[gt_james]

What was peak power on the SUs? Does anyone know what rpm the all stock from factory RX7 delivered the peak power? (~115 depending who you quote)

[KiwiDave]

Peak HP @ 6000rpm. I believe 113/115 are actually PS figures rather than BHP but i've seen them expressed as both. Factory sticker says PS.

[ian65]

this has all lost me.... did you get a BHP figure at the wheels Dave?