BOOSTD 7

He said for over 3000rpm ... meaning a 3000rpm spread. From 5200rpm past 8500.

That dyno graph gives me an erection ... if you were wondering

moespeed

He is talking about the span from before 5500 to 8500 RPM.

WackyRotary

I got it. Wide power band is more important peak power yes. BoostD 7, that graph makes me a little excitied too. he he.

peejay

Too bad he only started at 4500! (I assume the diff. between 4500 and 5000 is the time it took the turbo to spool up? 150lb-ft sounds like a good number for a N/A)

HWO

those numbers are from the dyno sheet you sent me right Cris? that motor had a T72 on it right? thats a a larger turbo than a T04/60-1 type set up, you'd have more HP and torque lower down than with the T72 right? - just wanting to clarify things for others, no doubt they will be asking

crispeed

Ok here's the set-up!

88 Turbo II Motor with a huge street port and small bridges on the secondary(outer) housings. Rotor housings relieved for the bridge port which by the way I happened to believe is the only true way to gain the maximum benefit of the port.
The turbo had a 60-1 compressor housing that was machined for a T-70(70mm) compressor wheel and on the turbine side a P-trim with a 1.0 divided housing. The exhaust manifold(turbo header) was also a divided design using a HKS wastegate.
Here's the really trick part about the set-up! It was runnning a modified version of the J-Tech lower intake manifold but with a Holley carb I modified for Blow-thru operation!

crispeed
87TII
9.20@150mph
--> fullboost.com

buzz

OK Crispeed... a couple of quick questions;
what size was the holley and was it operational (ie did the fueling or was that external and the carb was simply used as a really big throttle body?)

are there any pics of the set up?

any do you feel that bridged primaries would have given any additional power?

and finally, when do you go back on the medication... - that is a crazy sounding set up! (nice pics on fullBoost too, by the way!)

qwck10th

I agree, crispeed is da man... and I'm listening...[quote]...Rotor housings relieved for the bridge port which by the way I happened to believe is the only true way to gain the maximum benefit of the port.

I just did some "trial fitting" of a rotor housing over my bridge port, and sure nuf, there's about 1/8" of housing overhanging the bridge port. Looks like I can take that bridge cut all the way to the o-ring support, and through it if I seal it well... probably wont do that though. Hmmm.

Anyone want to comment on what the relief cuts might look like... Any examples floating around?

Thanks again for the insights C'speed.

All best,
Steve C.

Splortch

"BRAAP BRAAP BRAAP BRAAP..." Do it!

buzz

qwck10th - got a copy of the Racing Beat Manual (if not - then get one!) or "How to Modify your Mazda Rx7" from HP Books by DAve Emanuel with Jim Downing? Both have nice shots of what you are trying to do. Sorry, I don't have a scanner

WackyRotary

Mazdatrix has pictures of this on ther website... I think in ther how-to section

SPEED_NYC

iTrader: (3)

anybody??

Judge Ito

Love that noise!!!!!

InfiniIIIREX

a bridge-ported rotary at idle is to Japan, as a big block muscle car camming at idle is to the US

Roland

test

RETed

Too many people get caught up in too much hype...

Don't go crying when the bridge cracks and takes out your whole motor.

Sure, peak power numbers are nice.&nbsp A street port motor is going to beat the BP motor up to 4kRPM.&nbsp I'd like to see this proven otherwise.&nbsp I've never seen a BP motor put out 200hp before 4kRPM - I've seen streetport motors do this all the time.

Porting is like cam selection - there's a trade-off.&nbsp Enormous overlap and increase intake duration shifts power curve upward.

If you can handle the higher RPM power curve, then go for it.&nbsp Remember, you get very little power down low.&nbsp This really means if the car came with a stock ECU, it's a TOTAL WASTE OF TIME trying to BP such a car.&nbsp A BP motor should either be distributor or stand-alone EMS that can let the motor rev up to and past 9,000RPM.&nbsp This is where the BP motor shines.

For a road race car, I'd stick with the streetport, unless you KNOW you will keep revs up high.&nbsp Road racing usually implies broad power curve - this is not something a BP engine has (unless you can extend rev limit).




-Ted

RICE RACING

Dude, these are the facts !

If you road race the BP will not be as laggy as the side port, END OF STORY !

I know, I road race a street port and it makes 400 to 500rwhp (dep on boost) and it's power and torque have narrow ranges compared to a motor with overlap.

This has ALWAYS been the case for all types of engines.

I do not care if you road race, drag race or street race, you're revs will NEVER be below 4000rpm ! BUT FROM 4000rpm to redline YOU WILL ALWAYS HAVE MORE TORQUE & POWER WILL BE BROADER than ANY side ported engine...period.

ONLY ONLY ONLY ONLY downside to partial BP is cracking, simple solution partial PP. The only other issues are that for true street daily driver low speed fuel consumtion goes up 30% or more and they tend to be more noisier.

In summary, more overlap is better for performance, street ports are Exactly that STREET PORTS...they can be made to go realy well but In fact for THE SAME POWER LEVELS AS PORTED (BP or PP) ENGINES, THEY INFACT ARE UNDER MORE STRESS !!!! A BP or PP (partial) will have a larger power band and will suit a std gearbox better than a highly tunned side port.

So if you are going to race, and fuel consumption (low speed) and noise are not an over important issue then you will get better performance from a partial BP or PP engine from any revs above 4000rpm.

RICE RACING

Pretty much ALL of that is just wrong !

SCOOT make max power at 7400rpm with a partial PP (700+rwhp of it) My PP has made ALOT of power at these revs as well. Lots of other people I know with Partial BP's make max power below 8000rpm (well below) My highly tunned side port needs around 8000rpm to make top power and it is very narrow compared to a BP or PP.

The torque shifts DOWNWARD with a BP or PP and ther is ALOT MORE OF IT, MUCH MORE. than a side port. Along with this a majority of BP or PP partial or full I have seen make full power by 8000rpm. This reving over 9000rpm is bullshit taken straight out a RACING BEAT catalogue ! and in no way applies to partial BP or PP engines based on REW or T2 blocks and Intake manifolds. The facts are that you need to do specific exhaust manifold tunning and Intake tunning to get the 9000+ rpm @ peak power, I KNOW I HAVE DONE IT ON MY FULL PP TURBO.

RETed is right in that it is not a mod to consider for someone who is not going to change ECU/Turbo/Injectors/Most of Car!! It is the last step in rotary performance, however it is THE BEST STEP for racing..........THIS CANNOT BE ARGUED

crispeed

Hey Peter!
Ever notice that most of the people who complains and condem something are the ones who have actually not even tried it!

crispeed
87Rx-7 TII
9.20@150mph

Megaspeed7

I have been in rotaries for 6 years now (just got back into them after a 1.5 year break) and have had 5 2nd gen cars so far. I have NEVER rebuilt a motor (I am poor college student/mechanical engineer intern w/ baby and wife) but I am planning on tearing mine down and rebuilding this summer. I have a 60-1 turbo with a .96 undivided and P trim turbine wheel with an HKS AIC, Greddy manifold, etc. etc... (these mods are sitting on the floor right now- not on car YET).
Anyways I have been researching what kind of porting I wanna do on my T2 block and I think I have come up with a strange/neat solution that I dont think anyone has tried as of yet. What about a hefty SP and a partial PP with their own set of intake runners with some butterflies in them (to switch on at high RPM) like the 6 port motors have? Wouldn't this be the optimal setup for a car that would require daily driving and also be a weekend warrior? I know it sounds alot like VTEC, but wouldn't you guys think that this setup would have the best power curve? You could get an rpm switch from summit (or run it off the haltech) and run some vacuum switching valves to switch the Periph Ports on for some MAD top end (since you will be in the positive pressure range anyways at 4-5k rpm). Am I dreaming too hard here, is there something that I'm missing? Just some food for thought.
Later,
Patrick Harris

RETed

This car is an interesting example, as it runs stock primaries by PP secondaries.&nbsp Who got the resource for such a set-up with that custom cast intake manifold???

I still stand by my claim that a BP makes CRAP for power under 4kRPM.&nbsp I haven't messed with a turbo BP, but I've toyed with an NA BP.&nbsp I don't build motor that have high, peaky power bands that brag of high horsepower numbers.&nbsp 99% of the motors I build are for street cars which have no use for bridgeporting.

Not from all the Japan dyno graphs I've seen...
Comparing BP versus SP graphs, it's obvious that the SP motor makes a LOT more power (area under graph) under 4kRPM.&nbsp That was my point.&nbsp Overlap kills low-end power - this is straight out of the Racing Beat catalog, but it's also support by EVERY OTHER ENGINEER THAT DOES ENGINE ANALYSIS.&nbsp Go read the SAE papers if you don't believe it.&nbsp Exhaust gas dilution of the intake charge is a FACT; this is something you cannot argue against.&nbsp Anyone who knows cam profiles has a clue on what overlap is - it's the same with rotary overlap.&nbsp What has changed?

Are the Japan tuners doing something wrong that you're doing right?
I know you BP guys have dyno graphs floating around - maybe you want to post the URL's or pics so we can see for ourselves?



-Ted

peejay

RETed, it's funny you should mention boingers... making the LDA smaller (increasing overlap) generally brings more midrange power for the engine at the expense of idle quality and low load economy.

RICE RACING

That's the thing RETed, I do not think any one in this section of the forum is "that" interested in power below 4000rpm...............

But power/torque, spread of power/torque band and throttle/turbo responce All improve by quite vast margins @ any revs above 4000rpm. Which is where a majority of people end up being if you do the analysis of any type of racing road/track/strip.

So long as you can handle the negatives (mentioned) and for you're "honest" application the positives of race porting are there for the brave few who are willing to try it.

You need the money/equipment/knowledge either direct or indirect to run/build a "race" ported rotary, but once you do it when set up correctly (i.e. not run with "true" road legal exhaust system) and revs above 4000rpm a 400 rwhp race ported motor will be nicer to drive (faster accel & spool up & less peaky in delivery) than a 400 rwhp street port. Lumpy idle and noisy exhaust will get you ALOT of attention when you take it down the shops though

RETed

See, that's the problem...
I mentioned if you can honestly keep the engine above 4kRPM, then I see no problem BP'ing the engine.&nbsp The hang-up is that you cannot guarantee this for EVERY track you go to unless 1) you're restricted to certain tracks, or 2) have the ability to change your gear-sets.&nbsp I've been on tracks where due to the stock FC gearing, the revs drop below 4kRPM (Laguna Seca Turn 11 is a good example).&nbsp First gear will end up redlining the engine out of the turn (and adding an extra shift), but a stout 2nd gear is more than enough to pull out with decent power.&nbsp Going into 60mph through Turn 11 means you've got one helluva good suspension, or you need to slow down...

Road racing throws a lot of variables at you.&nbsp I'd rather have the wide power band and give up some of the top end on a track I have no too much experience with.&nbsp Torque gets you out of the corners quicker.&nbsp We regularly chase full-race Mustangs that pull the hell on us 200-300hp FC's out of the turn, but we easily catch them diving into a corner or going through a transition - they have double the power!

The thing that irritates me is all the people who just want the "brap brap brap" noise, but have no clue what thay are getting themselves into.&nbsp This is why I question each and every BP post that pops up - I find it unnecessary for 90% of the people who are on here.&nbsp Most of these guys won't break 300...400hp on their cars.&nbsp Why would you want to BP your engine with only 300hp as a goal?



-Ted

MikeL

I finally got to drive my BP TII today. It's bridge ported on both the primary and secondary. It feels great. Pulling away from a light, I'm near 3.5k rpm by the time I get the clutch fully engaged so, less power below 4k shouldn't be much of a problem.

I have only 25 miles on it right now so I can't really boost or wind it up. I wasn't used to it today and when I left a light as normally as I could and got into 2nd gear, it wound up from 4k, where I was planning to shift, to nearly 5k before I could react. I was paying more attention to the boost gauge than the tach, I guess. I hit 1.5 - 2lb boost. That's when I realized what rpm I was at.

I think it's gonna be just fine for me. From what I've seen in my short drive today, there's a lot more torque from 4k up and, that's with me trying to not boost.

Mike