VaSSagO

G'day all, been awhile since i last posted but thought this might interest a few of you.

I have a
S1 Rx-7
13B 4 port motor with stock porting and a 12A carby, (thats how it was when i bought the car),
Extractors, 2 1/4 exhaust with 2 mufflers + hotdog and no cat
Lightened Flywheel
Removed A/c
Removed most emissions (i think)
Brass Button clutch
RamFlow Air Filter

I then had this dyno done, it was about a 30'c day and was done in 4th gear. He then changed to 3rd and did it again as the dyno cant go higher that 200km but that run got an even lower figure...104rwhp by memory.

VaSSagO

After that dyno I hooked up mechanical secondaries on the carby, slightly increased the accel pump shot (will increase it more this afternoon). Then $110 for 2nd gen leading coil setup....another $100 to install it and $20 for new leads. Put on 2 new Craig Davis thermo fans and removed the stock clutch fan, that set me back $200 and then had the car "dyno tuned" that was another $55. (Was not impressed with dyno tune, all they did was 'power tune timing' for $55, increased power by 7rwhp).

But look at the difference in the graphs...much smoother now (this one was done in 3rd) and especially the torque from peak of 420 to flat over 600lb. I think the biggest difference to power was from the mechanical secondaries, thermo fans and dyno with ignition made only real small gains.

Pedestrian X

are you sure its a 13B dood?

wwilliam54

looks like a 12a to me

10sec rx7

Guys,

its a dyno dynamics dyno they read around 15-20% lower than your dyno jets.

Dale

Pedestrian X

WELL THEN THAT EXPLAINS IT!!!

thnx :]

KYPREO

interesting stuff...pity it wasn't done on the same dyno.

I'm about to get a follow up dyno run after mainly carburettor and timing mods.

123rwhp isn't too shabby from a stock port 13B -pretty good actually - and you're right the torque is very flat. I know of extend ports running modded nikki carbs making less power.

KYPREO

and ignore the torque improvement because you have done the second run in third and that will increase rear wheel torque from fourth by around 30%.

VaSSagO

damn........well from peak of 420 before to over 600 now is almost 50% gain and nice and flat aswell. Took her for a drive this afternoon in the wet......quite happy......almost lost it flooring it in 2nd then in 3rd still had no traction and pulled off before i had the same problem (ending up on the other side of the road). Both the runs were on dyno dynamics dyno so in theory it shouldnt matter unless one is out of calibration. The guy at rotomotion said it was a quite good power for a 12A carby on that motor but could of got higher with 13B nikki or webber.....but by the sounds of it be $$$ for small improvement, looks like I cant really do much to to the engine without going to either webber and porting or EFI and a turbo both look like big bucks for a uni student.

KYPREO

I'm a uni student too, I know what its like.

Ok...if you wanna compare torque...ignoring the difference in frictional torque components in the gear themselves (which might make 1-2% difference or so, as you found in the first dyno run), the torque difference will be 43% at any given rpm (third is 1.432:1, fourth is 1:1). So the run in third will be roughly 43% higher in torque than in fourth. The second run peak was about 700 if you look at it, which if it was in fourth ignoring difference in gear friction would be around 490ftlb. This still represents almost 15-20% gain...very healthy gain.

I don't believe a 13B nikki would give you more power...the RX7 12A nikkis can actually flow more air and fuel. A webber would give you more power, but not much, given they are stock ports.

VaSSagO

Thanks for that info Kypreo.

Would increasing the size on the secondary jet on the nikki make any difference, the 'mechanic' at rotomotion seemed to think it was running the right fuel air mixture as it was, but i find that hard to beleive it was running perfect considering it had not been adjusted since mechanical secondaries, ingition system redone etc. but i think he just wanted the next person on the dyno and couldnt be bothered.

Also here is a pic of my car.......what do you think....will she be able to pull off a low 15sec 1/4 mile?

VaSSagO

BTW Kypreo how are u getting 119rwhp from a stock untuned carbi on a 12A with a cataylitic converter??

In comparison to that mine is low for a 13B

KYPREO

Yep, I reckon you could pull a low 15. Mate of mine with 110rwhp s1 just did a low 15 at calder.

Every tuner has a different opinion on what a/f ratio is best, but I can tell you the guy who built my 12A carby used bigger secondary jets.

My power figure was achieved at 7800rpm. The catalytic converter is a hi-flow unit rated up to 400hp, so it would make no diff to power. The exhaust is also straight through - no baffles or offsets whatsoever. Its a series 3 12A which came out with much larger ports than your 4 port 13B. Also, it depends on whether your 13B is a turbo block (lower compression) or an RX4/5 type 13B. The single biggest factor in that power run was the Davies Craig electric water pump and thermo fans, which i reckon was good for about 15rwhp. With the modded carby and cold air intake, I'd be happy with another 10% on top of the 119.

VaSSagO

It is a turbo block i have been told. I have the thermo fans.....didnt notice much difference with them. Does the elec water pump make that much difference?? Would a straight through exhaust lets say 2 1/2 or 3 make much difference, mine is already really loud, it sets off car alarms and mates can hear me coming a km or 2 before i get to there house if i floor it. Also i haven't installed a thermo swtich yet, would that make a resemble difference??

VaSSagO

The mechanical secondaries, thermo fan and ignition upped my hp to 116.9rwhp, the red line on the graph from 109rwhp sothe thermo fan can't make that bigger difference.

Maguire

iTrader: (1)

why does the first graph say mx5?

VaSSagO

Cause some people dont know the difference between an Rx-7 and a Mx5. Either that or i converted an mx5 to a Rx-7 in 10 days.......look at the number plate in the customer section is the same. (1BAD624)

KYPREO

OK, I'll try and answer everything....
13BT block will have less power than a RX4 generally as the compression is lower. It also depends whether it is series 4 or 5, as series 5 had 9.0:1 compression (s4=8.5:1, rx4=9.4:1) and also lighter rotors. In a stock port engine, the higher compression could be worth 5kw or so.

EWP makes a huge difference....a mechanical pump saps around 12-5kw (engine) at 8000rpm difference! water under 14psi of pressure offers a lot of resistance. I have completely deleted the mech water pump - there is one belt running from the e-shaft to the alternator. I offered 15rwhp/11rwkw as a conservative guess of the combined effect of EWP and thermos. It could be more. thermos make a small, but noticeable difference, but mostly at low rpm when the clutch is normally engaged (clutch fan is spinning at much slower speeds above 4000rpm). Even then the fans are only being dragged by air.

2.5" from 2.25" wouldn't make a huge difference, but straight through definitely does - especially at high rpm. Exhaust is really the key to high-rpm power. If you are already too loud, then you either should leave it or use some better mufflers. I have three (all straight through). 3" is overkill for stock ports. Extractor design is also important.

Thermo switch will make **** all difference power-wise (.5kw? from the 10A or so load), but it will be nicer to drive, as the alternator will only be loading up when the car is stationary (no ram air flow to keep radiator cooling). It could make a bigger difference if your electrical system is struggling.

VaSSagO

Thanks for that......answered alot of questions i had. Maybe time for EWP and new straight through exhaust next time i get some money spare. Can go in the list of things that i need/want to be done to my car.

Directfreak

iTrader: (2)

DO NOT GET AN ELECTRICAL WATER PUMP FOR STREET (DAILY DRIVER) USE.

I hope that was clear.

VaSSagO

Not really......how come....waste of money?? unreliable??

KYPREO

You don't get Davies Craig water pumps in your neck of the woods. Mine has been running 2 years...daily driven, no issues. In fact, outperforms factory cooling system, and as I said, plenty of power gain. It is not like the Moroso water pump - it is a universal pump that can pump 80L/min and is installed on the bottom radiator hose.

These are being used on at least 10 rotors in Australia that I know of.

DO NOT BAG A PRODUCT YOU HAVE NOT TRIED.
By the same token, I would not recommend a product that I couldn't stand behind personally.
I hope that was clear.

Rotortuner

Do you have a link to where i can see or look/buy one of those electric pumps?

CJG

KYPREO

www.daviescraig.com.au

VaSSagO

Went to the local auto parts store.......$210AUS for the Craig Davis EWP, a bit cheaper than the RRP of $350 or something advertised on their site.

Also spoke to performance exhaust place, he recomended 2.5inch straight through with 2 cannon style mufflers. Would this be an ideal setup for NA 13B? How loud would this be, especially considering no cat? Is $400 aus a resonable price considering he will cut the extractors a bit shorter and put in a flange to make it 2 1/2 all the way through, using mild steel and the 2 mufflers are supposedly good American ones, he mentioned the naem but i can't think of it now, it was a name i hadn't heard of before.