BoostedRotors

While obviously I agree that a rotary is far more responsive to exhaust upgrades than a piston engine, I do find it hard to believe that an NA rotary will have greater than a 15-20 hp gain from exhaust/ intake...which in itself is an impressive number.

I searched this site for dyno sheets of a BPU NA and the only number I saw was a 12 hp gain on an NA...and I scrolled through 6 pages. I saw a lot of others claim more, but the only dyno sheet I saw to back any of it resulted in a 12 hp RWHP gain.

Id love to see a dyno where an NA gained 40 hp from exhaust alone, not to prove me wrong, but to prove everyone else right. I am in no way downing NA rotary cars, im just trying to be realistic.

---Nick

redstreak

I'm sorry I just had to reply to this one.

I work in marketing and if my company ever claimed that one of their products was 28% better than the previous version it had better be 28% better than the previous version otherwise that is false advertising. I am willing to bet that after they stated the 28% increase it also says something to the effect of "installed on a car in good working order". They most likely have a dyno sheet of a car that they have installed it on yielding a 28% increase, if I was Mazdatrix I would, and if I didn't I would make damn sure I was getting one. False advertising is a very serious offense and that sir can not be classified as a Marketing Gimmick.

redstreak

Damn should have read a little further down before I posted, well there you have it.

Evil Aviator

Yes, they are lying too. It's all just a conspiracy to make us think that an RX-7 actually has a chance of beating a V-6 Mustang. Those exhausts acutally cut the RX-7's HP in half, so don't bother putting them on your car, and just accept that fact that you will never beat a V-6 Mustang.

rxspd

lol

Scott 89t2

edit: never mind....


does it say the dyno runs were the same day, same temp, and same gear though? it's easy to fake dyno runs by changing those.

AbecX

The guy that posted it is the one thats causing all the flaming, I'm not trying to flame any of you guys, anyone that actually likes car's for speed of any kind is ok by me, but claims of 28% hp increase, HEH. I am wondering why they didnt just go the way of K&N or flowmaster, or hell, even that vornado thing and say it adds up to 10hp, its the "adds up to" part thats the catcher, that mazdatrix crap is full of it unless it was on a car that was 75% more restrictive then the stock exhaust, doubtful.

tims

Mazdatrix is a reputable parts company that could not afford to use any false numbers in their advertising. All their competitors would hammer them if they made it up. but chassis dynos are the easiest dyno to fudge the final number on. all of these dynos have some sort of correction factor that is suppose to compensate for changes in temperature and barometric pressure. Dyno operators have become very skilled at manipulating these correction factors to yield higher HP numbers. In this situation I would tend to believe the power output numbers. I have seen very well built and ported race motors gain big HP numbers with some exhaust work. even after the engine builder said it would not help at all. just changing the existing header/exhaust system a little gained more than 30%. I would guess that the peak HP increase is high in the rev range and may be unusable to a street driven car. so the the useable increase may only be 10-20hp. this is also at the expense of smog laws and noise. Mazdatrix is not my favorite shop in town but I doubt they could make up these numbers and be allowed to use them for long.

AbecX

Thanks Tims. I could see it gaining 28% in a rotary engine thats been ported and made to rev to 9k rpms.

But answer me this so we can end this discussion with everyone else. In a stock 2nd gen rx7, will just by adding full exhaust add anywhere near 28%, which would be about a 30rwhp gain, in a N/A engine?

The Ace

Man you dont seem to get it, do you ?

Even on my TII, just adding a K&N cone and a catback (pre-cat and main cat still intact) gave me almost 30RWHP more. That is (in case you cannt add or multiply, which seems to be the case here) 30/160*100=18,75% increase in WHP.

And I havent touched the main power-shappers, the two cats. Simply removing the pre-cat (which is useless anyway) has NEVER yielded LESS than 10%-15% in any TII I know of...more often than not closer to 20-25%.

And yes, all this applies to NAs too, since the rotary engine responds differently (see: "Better") to exhaust gases velocity, turbulence etc etc.......

VetteKiller

Yes

SaabGuy

All I know is that my car when stock puts out 183hp at the flywheel.

I upgraded the turbo slightly, GN compressor but only 6psi of boost. I also have a complete RB turbo back exhaust system and a few reliability mods such as fuel pump and SAFC which really does nothing but save the motor.

Now I have the dyno sheet posted on this site somewhere so you can do a search if you want, but I pulled 203.5 hp at the rear wheels. 15-20% drivetrain loss says that I've got 240-250 at the crank shaft.

I'd say RB's full exhaust claim of 59HP is on the money.

AbecX

Hey geniuses, I said N/A not forced induction.

And your full of **** to think a N/A will get 30Rwhp from exhaust.

SaabGuy

Oh come on now. you are just jealous.

Think about it though.

If company A hasnt got a clue and claims that thier expensive POS exhaust system adds 30 RWHP, what do youthink a real company would do? Advertise that their **** only makes 12hp?? NO they are all in competition. And the truth of te matter is noone will ever sue them becuase thats not really the American way. Also, not many people go get their car Dynoed

AbecX

hehehe, I am going to take the rx7 I bought to the 1/8 mile, I am expecting 10's out of it

rxspd

Abec, just get your 7 running, put get a muffler shop to build you some true duals, and get some hi-flow mufflers, and see for yourself,or are you to retarted to figure out whats wrong with that thing?

BlackRx7

you guys are missing the piont, when you open the exhaust on a turbo anything you will see larger power gains than an N/A, just a fast exhaust is moving faster, so its spinnin the turbine faster. Now I know from expericence my 89 gtu I had owned had no cats, a bonez air filter, header and straight through mufflers, and lemme tell you I could bearly feel differnce, it was there but minimal, prolly no more than 15hp with all those mods.

I ran a 16.76 in the 1/4 when all I had were crap pace setter mufflers

with bonez air-filter, not cats and ss straight through race mufflers I ran a 16.35

I was pretty pissed for spending all that money and only nock off 0.4 sec off my time,

AbecX

It runs already

rxspd

Why do you even have the car if you hate them so much????????

AbecX

I never said I hated the car!

blu_gxl

i know they had a link to dyno sheets a while ago.

exquivical

"I ran a 16.76 in the 1/4 when all I had were crap pace setter mufflers

with bonez air-filter, not cats and ss straight through race mufflers I ran a 16.35 "

You either had a POS or you can't drive.

AbecX

He probably lived 5000ft above sea level!

Seriously, 16.3 sounds about right for a car that puts out an amazing 100#'s of torque at 3000rpm. Post up your MPH BlackRx7

wpgrexx

if thats all the gains he got, there is something not right on his car.

exquivical

OR something is not right with his driving - Remember, no matter how fast your car is, if you can't drive it, it means dick.

I had an '88 with a bonez straight pipe with a built-in silencer, cone intake, and some dynomax straight thru mufflers. With the countless laundry list of races I had over a 2 year period, my geustimate of a mid 15 is not a number just thrown out into the air.

My GSR went 15.60 with a short-ram intake and stock crap michelin tires. I raced my brother (whom I sold the RX7 too) and beat him by a few car lengths because of his poor driving.

A good running NA (key terms - "good running") with a straight pipe and straight thru mufflers should net a mid to high 15 with a proper driver. Like Abecx is touching base on - just compare your trap speed with someone with a faster time 1/4 mile time along with your 60ft times, and you should be able to determine what your car is capable of.