how much power from stock internals
 

okey - only bolt-ons, no cracking open the motor...

how much power could one get out of a 12a with relatively easily located items?

Max is considered to be around 150hp... assuming you mean n/a and no nitrous.

150hp is the theorized number on a stock port 12a. I have only seen one dyno sheet that shows more than that, 153hp with a Yaw power carb tuned by Paul for the sake of maximum horse power on a dyno.

Ryan

And how would you achieve such a figure? Im working towards that myself :).

~T.J.

Simple MONEY!!!!!!!!!!!!!!!!!!!!!

Dual primary exhaust $700
Yaw power $350
Proper fuel delivery for the above carb $250
Underdrive pullies $110
Electric Fan $200
Some sort of direct fire ignition $150

So you could probably do it for $2300-$2500, including a set of jets for the carb and ample amounts of dyno time.

150hp is not a bolt-on number. You must do a lot of trial and error tunning to get that number.

Ryan

Your estimate is way high.

You can make your own exhaust for much less than RB... won't be as quiet, but oh well.

Proper fuel delivery will NOT cost that much! Pump/regulator $75-80, then you need a gauge. The gauge will not cost $170!

I paid $110 for my fan. You can get better ones cheaper.

No need for underdrive pullies. The HP gain from removing the belts entirely is minimal (maybe 5hp) so the teoretical gan from an underdrive pulley is so low (maybe 1hp? maybe .5hp?) that it's not worth it and you'd be better off spending the money elsewhere.

Direct fire not necessary - the stock system will do. It'll just make life easier. (My setup, by the way, cost $250, not counting the greatly reduced spark-plug life)

Peejay

Please describe in detail on making your own exhaust.

You go to your local race shop with flanges for your engine bought from Mazdatrix or RB. You should have already talked to them about primary diameter and length plus collector dimensions before you go there. Tell the fabricator to use a heavier gauge material for the tubes than he would use for a boinger. Peejay's strength is that he already is a welder if I remember right. (or was it pele?) The cost for such a header will be under $200....you could even push for $140 and get away with it. After that point, any muffler shop can complete the rest of the system. If you do go the custom fab route, I highly recommend you send the piece for a JetHot 2000 thermal coating. Stuff lasts forever. Cost me $110 when I did it, but that's going back at least 7 years now. The header coating outlasted three cars....:cool:

is that 150 hp at the wheels or estimated crank power?

i want to shoot for about 120 at the wheels, any suggestions?

The 150 figure is at the flywheel...

The 150 max is with a nikki carb, is it not? Strap on a 48IDA and youre going be capable of more power than that.

JetHot2000 is now $200 + shipping to coat a 12a header. I'm sending mine out today.

Fabbing your own exhaust can be cheaper but will it last? That RB dual exhaust system is sturdy and solid. Will last a long time. And it fits right too. Tested and tuned, a true bolt in.

Underdrive pullys are used in road racing where you spin the motor over 7000rpms all day, so the water pump doesn't cavitate and the alternator doesn't get overspun. Not needed for street. The RB dual sheave main pulley is very nice, has timing marks on it already, and is smaller diameter to reduce water pump rpms, but you don't need both sheaves if you go electric fan and remove smog pump.

-bp-

the 150 is the max the ports on the engine can handle, not the carb

My "header" was fabb'd at Rotary Performance of Garland, TX and sent out for the coating prior to installation on their hi-po rebuild of my 12A. That was in '94 and the header still has no holes and is structurally sound. It has outlasted 3 cars. If it's built of heavy gauge pipe, it will last because of the coating... :cool:

That's right, once you hit around 150hp the restriction becomes the stock port size.

The best way to 150hp (w/ stock port) is a good carb, proper fuel delivery, and exhaust. A little timing advance doesn't hurt either. Don't worry about fucking with your ignition, it doesn't matter; the stock system works just fine.

With a ported Nikki carb. Like a Yaw power, not a stocker.

Ryan

Nope, not with stock port limiting things. But if you're talking about a wild ported motor, of course the IDA's gonna be capable of better power.

What about the same question but to a 6 port 13b retaining the stock RE-EGI? :)

I dunno about fuel injection, but I've heard that a stock-port 6 port 13B makes about 180hp with a good carb. I imagine stock fuel injection would be less due to the restrictive AFM, but I don't know shit about SE's.

Stock ports of course, that's what this thread is all about. I think the ports are capable of more so let's see some proof.

Well, I dunno... I've got a 48 DHLA Dellorto, and RB dynoed it at 154hp @ 7000rpm. Factor in that RB's probably being a little optimistic, most motors make about 150hp or so I hear. A Weber 48 isn't gonna be much different from a Dell 48 with a stock-port motor. So how do you think the IDA's gonna make more than 150hp?

See, the 150hp figure is pretty much the word as far as I can tell, representing the maximum that the stock ports are capable of flowing. If you say you think there's more there, you're going against the respected opinion, so let's see some proof of that.

Its not just a flow issue with the stock ports... Remember, porting also affects intake/exhaust cycle timing and duration. THAT'S where most of the power comes from...

mwpayne the description that peejay was talking is what i did in my car. LOOK ON MY SIGNATURE!!!!

You are correct. However, we are discusing the power potential of the stock port size, shape and location of a 12a. A stock motor, if you will?

I still believe that 150 HP is the magical number. All of the numbers generated above that have been on motors with tuned exhaust, and have been set up specificly for testing the limits of the stock ports, or for generating sales material.

Does anyone here have a dyno sheet that shows more than 125-130hp at the wheel for a stock port 12a? I only hit 112hp at the rear wheel with a stock Nikki.

Ryan

A guy after my own heart...:p:

That sounds like what I'm aiming for. Then later I'll add a supercharger. Woohoo!

hey ryan - i know i've asked this before but what mods have you done?

worn oil seals, i know that - hehe. full RB exhaust, no rats nest, electric fan. anything i'm missing?

if that's it, 112 is pretty impressive for the cost invested in mods.

is removing the rat's nest good for any power, or does it just eliminate various problems?

you gonna run at everett this weekend, btw?

/edit: now that i think about it, it seems weird that i'm asking all these performance questions after being on the forum for an entire year. all boils down to the fact that now that i'm confident in my little motor, i'm ready to start removing the shackles as it were.

There is minimal evidence that the average stock 12a will get 150hp at the flywheel with the usual header/exhaust and carb mods. It is possible with very extensive tuning and hours on the dyno. But how many 12a engines are tested that way.

Rear wheel readings is what we normally get and readings between dynos is significant. Most likely the reading is in the range 110-120 hp. What really matters is not the inaccurate measured hp but the impact on the 1/4 time as a stop watch is really accurate.

Addind a header/exhaust, modded carb and intake, taking off the air pump and adding a K&N filter knocked 1.8-2.0 seconds off my time. My best estimate is that indicates an extra 40-45 hp at the flywheel.

The port sizes are now the limiting factor. Adding a better fuel pump, carb and ignition will not pass that barrier. Port the engine, and its potential now with these improvements may give 40hp increase.

is there a common AFM that people swap on the EFI motors or is everybody a carb lover?

No, a stock carb can do it too, if it's tuned properly.

There's a dyno sheet on the Yawpower site detailing a Pro7 engine, making 151hp. That is entirely through tuning - Pro7 says no carb modifications allowed except for jets (he modifies the air bleeds too but they're not allowed to be adjustable), stock ports, stock internals, stock '81-5 manifold with shutter valve in place, and stock exhaust manifold with 2.5" pipe (no muffler) !

I find that hard to believe... from Yaw or anyone. If it is indeed true, I bet there's more than meets the eye to that setup.

I wonder if he has his special exhaust port tongues in there :)

Among other things ;)...

Pro7 rules are strict! :)

Besides it was Mazdatrix's engine! I doubt there'd be any "funny business" going on in there... it would seriously hurt their reputation as racers and engine builders if they were found to be cheating!

True, but you have to admit that a stockish (with different jetting and minus muffler) 12A RX-7 making 151hp is highly unlikely. I'm not saying it's not true, but most Pro7 guys could only dream of getting that...

Yeah but how many Pro7 guys are running engines that they grabbed from a junkyard, with no jetting changes, with stock fuel systems, etc?

That 151hp is from a heavily optimized carb (to the letter of the rules) and fuel system and a 100% new engine.

Seems like alot of work for Pro7 lol... looks good on Paul's site though.

It might be possible on a perfect engine. I have never seen a set of dyno figures for a range of stock 12a engines but think plus or minus 3-, 5% could be possible.

For example over 30 years ago I was involved in works Mini Cooper S cars. Engines within tolerences were plus or minus 5% output from standard. Only 1 in 100 cars came together such that they were a good basis for competion with all the legitimate variations coming together in an optimal way. Minor variations in the head casting were critical and only 1 in a 1000 were selected for a hand built motor. It was stilll a 'stock' motor!

ha HA!! Only 150? I talked to Stan at SDJ Motorsports (www.sdjmotorsports.com) and he builds ITA legal engines (stock porting, specified carbs, no porting manifolds or anything like that, etc..) and with some very restricted rules to work with, he's gotten like 172hp at the flywheel on his complete setup.

Now if he could use ANY intake manifold and ANY carb he wanted, I'm sure he could come closer to 180 or 190.

And then the fur started flying...:p: Saint's alive, begorrah!! :cool:

Leason number one kids, how to say BULLSHIT, with the flag.

:bsflag:

I'm calling your bluff, bust out with dyno sheet!!

BAH! HUMBUG!

Everybody knows you can get about 275 horsepower from a dead stock 12A 1st Gen.

All you need is the "rice" stickers that say you do.
:gotrice:

Ok prof...

:bsflag:

How did I do? Was that good?

very good! A little slow on the response, but nothing to worry about. :D

if it makes any difference...... my 12a is stock port, piece'o'shite(i mean pacesetter) header and exhaust, dellorto 48 carb, accel coils.... guess that's about it. i made 3 dyno runs at the indiana rx7 meet, 109rwhp, 117rwhp, 117rwhp in that order. whatever that is at the flywheel, i have no idea

wow!

did you port the crap out of the header before you installed it?

I did a 113 rwhp with a stock Nikki on a RP streetport...anyone recognize the name Ari Yallon? Cats and everything to pass emissions...too bad it's a rotting carcass in my driveway, now...:(

Time to get out the... https://www.rx7club.com/forum/attach...&postid=830932 :D

Now for a little rant. :) When are you guys going to realise that dyno numbers are not the be it and end all?

Dyno's are an invaluable tool when it comes to tuning and guaging the effect of modifications. But, dyno numbers are not an accurate way to compare horsepower between different vehicles because results can vary so much from dyno to dyno... I know from experience as do the dyno operators themselves. The only way to get an accurate comparison would be to run both cars on the same dyno on the same day.

This is even more evident when comparing results between the common Dynojet dynos you seppos have and the superior load cell type dynos used over here. :D The difference is around 15-20%.

load cell type dyno = chassis dyno ???