what kind of exhaust is that?

 

v band at turbos. two 3 inch SS downpipes merge into a Burns Stainless 2-1 w a v band to a Borla 3 inch #40944 straight thru muffler w a Racing Beat CB.

downpipe area is 12.98 sq inches

standard 3 inch downpipe area is 6.49 sq inches
3.5 inch downpipe is 8.92 sq inches
4 inch is 11.76 sq inches. (all assume .065 wall tubing.)

that is one of the reasons i have 17 psi of pre-turbo backpressure at 15 psi boost.

howard coleman

 

Interesting stuff. Makes me glad I went with a full 4" turbo back exhaust. Car looks great Howard

 

just an update...

8700 miles on my twins and they are now in the barn for the wisconsin winter. sort of a bummer but a great time to rip the car all apart and play... this winter manual brakes, 13 inch rear discs, 2 or 4 piston rears and a Tilton adj balance bar.

oh, and a new clutch. i just shredded my Exedy Hyper single. as i mentioned there were lots of updates for 07... i am running methanol and just going nuts turning up the boost and not seeing any knock or egts...

the next to last run (before the clutch went south) the car just went sideways at 5600 in 3rd at 60% throttle. i am beginning to understand why i built it.









howard coleman

 

nice howard

 

Thats too cool what mazda turbo rotaries are all about (sideways in 3rd gear !)...

You have no power steering in your car howard? how does that feel? I am thinking of deleting mine for weight reasons, that and the AC

Again cool car !

 

Rice, I deleted my p/s and a/c back in the summer of 2002 (in texas!) and I have no regrets. I like the feel quite a bit, and the simplicity is a huge advantage in my book

 

 

manual steering is one of my favorite mods.

why they put power steering on a sportscar w 1450 front weight is beyond me. no matter what anyone says power steering negates most road feel. you might as well be playing a video game.

inspite of all the drag racers on this board the RX7 is a roadrace car first and foremost, properly setup nothing can touch it. ditch the power steering and say hello road feel. plus you get rid of ugly front weight. my car currently has 54% rearweight thanks in part to ditching the power steering, A/C, ABS, airpump, battery to the rear etc.

an added plus is you can change the plugs from the top in 5 minutes.

just a helpful guidence... do not remove your power steering belt to test "manual steering." it will drive like a truck as you are pushing the hydraulics and the steering w no assist. you need to lose the whole thing to get the true manual effect. i have been running manual since '99.

howard coleman

 

DONE ! The last few replies from people I respect are what I was waiting for I guess, I have all that crap in my car and want to see it gone asap... thanks again.

Oh, did you two modify the steering rack or coupling at all? (I will go read the procedure anyway).

I am removing air pump, AC, and PS ..... how much weight will I loose by this you think? Will also go no sequential once my turbo's arrive

P.S. No one here in aus does this mod, despite how much you all have written about it.

 

I'm guessing 30 to 40 pounds or so

 

A/c gone p/s gone (line looped.. Dont miss it a bit. G

 

Twins update...

finally, a transition from road tuning (do your really feel lucky?) to the dyno.

just a start.


2007..... Finally.

it has been a long time since my last on the road tuning blast Oct 23.

last sunday i buzzed up to Beyond Redline Performance in Green Bay (90 miles each way) to meet up w Luke Stubbs, proprietor of Wisconsin's newest and , IMO, most capable tuning shop.

on a sunday. no phones ringing, just Luke, my car and me.

the program was:

fix a longstanding high idle, tip in, better tune the vacuum and then the fun stuff. the first being tune on 93 gas to one bar. then tune 93 plus alcohol for one bar. finally let her really rip to see what we have inside those two TO4s around 24 psi w alcohol.

we started strapping the car down around 9 am and called it a day around 3...

and we completed a little less than half the program.

Luke being the smart guy that he is (you don't think i am working w an average tuner do you)... fixed the idle with some settings 1 stuff... diagnosed the tip in as not the usual accel inj or accel v TPS ( i knew that) and fixed most of it. then we worked on vacuum.

here is where tuning on the road and dyno radically diverge. i have done road tuning for 3 summers and being able to hold in cells in 4th gear on the dyno is wonderful. (everything was done in 4th giving poor old overworked 3rd the day off).

eventually we got into boost off the spring and then set the AVCR for one bar. while not anywhere near tuned out we made 408 rwhp and 321 ft pounds on the last gas run.

it was then time for alcohol.

using the same general settings except for lowering the pump gas as the alcohol fired we made 425 w 353 ft pounds.

none of the above is tuned out at one bar. i subsequently found a primary boost leak and a number of the vacuum to max boost cells can be improved both w re to timing and fuel. we only made 3 alcohol runs.

so there are no Marquis numbers here, yet, but there is data and i want to share it.

the plan is to be back on the dyno approx Aug 5. we should have lots of time to work on what we have and eventually run our 24 PSI and do 88 pounds of air.

i am really proud of my motor for doing over 20 4th gear pulls on the dyno and another 180 miles to and from and not breaking a sweat.

i am also VERY impressed w Luke. mark my words you will be hearing about him in the future. he is a very talented tuner. anyone within driving distance and wrestling w a tuning problem would do well to contact him.

Beyond Redline Performance. Green Bay Wi. 920-498-1223
Luke@beyondredline.com

here are the numbers from my 2 best pulls one 93 pump, one pump plus alcohol.

Gas
***************************************aver
EGT-------1214---1201----1204----1222---1286----1225 F preturbo
AFR------ 11.4----11.1-----11.0-----11.5---11.7-----11.34
Boost--- 15.3----15.5-----15.5-----14.9---14.7-----15.18
IGL ------17------17.3-----18--------18.3--------------19
Inj Duty- 75%---78.4-----81.9-----80.3---80--------79.12%
Knock--- 2.5-----4.0-------7.3-------4.0------5----
408/321

Gas & Alcohol

***************************************aver
EGT------ 1101---1110----1170----1187---1231----1159 F
AFR-------11.2----11.5----11.6------11.2---11.4-----11.38
Boost--- 16.7----15.9-----15.3------15.3----15.7----15.78
IGL------ 15.3----17.7-----18--------18.5-----19
Inj Duty- 53.1%--58.3----59.7------63.1----65.5-----59.94%
Knock----- 6--------4-------4.5---------3---------3
425/353

various items jump out... cooler egts w alcohol even w a slightly higher boost and more HP and Tq. lower duty cycle (of course). the motor isn't breaking a sweat in either run w 1550 being my target preturbo EGT.

to be continued...

howard coleman

 

YESSSSS!!!! i've been waiting to hear about your car again good stuff man

 

Great update howard, I'm jealous that you have a competent tuner so close by

 

What RPM are those timing values at?

 

i have a tuning thread ("80% pump, 20% methanol") in the Auxiliary Injection section where i am a moderator so i can edit it and was able to edit/add in the RPM as i figured it would be helpful...

the Power FC Datalogit cells are N16 thru N20 set at default numbers.
split was 11.

hc

 

Interesting read. I will continue to follow this. Thanks for posting the update.

 

I allways wanted to do true dual GT25's ever since Jason kicked my butt with his old M2 setup. I want to have a realistic street car that can fill up at any gas staion. But my qyuestion is: Why would you not do true dual exhaust (with X pipe)?

I'm not talking about fake duals that merge in to one then split in to dual. No, no one exuast per rotor all the way out. Besides gaining power, you could also keep the noise down with smaller pipes, twice the cats and mufflers. I wish I would have done it last year when I had the cash.

 

i always wondered if this can actaully be done (was about to start a thread too) but seeing that i wanted to go with a setup similar to yours but only on a 13bre it looks like tedious work....i cant say much....lol...congrates...

 

here's some additional data from the july dyno session which was the first time the twins were on the rollers...

next session may be this sunday and will run the turbos to their max at 25 psi on pump gas and methanol.

data snapshots at peak HP (6500) and peak Torque (6111)

i have included some additional digitally logged info.

AN2 is digitally logged Fuel Pressure.

AN3 is preturbo Exhaust Manifold Pressure (EMP). note it is 14 psi at peak hp and 16 at peak torque! near peak output my ratio is very close to 1 to 1.

actual accurate max boost on this run was:

-------n15.............n16..........n17........n18....... ..n19...........n20
------15.93..........16.85.......16.21.....15.40.......1 5.38........15.76

low backpressure is due to a combo of my exhaust ports, the fact i have two turbines and two 3 inch downpipes.

comparatively:

my total turbine wheel area:

2 X 4.522= 9.04 sq inches average ind & ex.

T4 O trim= 5.422
T4 P trim= 5.894
T4 Q trim= 6.646

additionally i have two 3 inch downpipes

area measured from the O D for comparative purposes:

2 X 3= 14.13 sq inches

3 inch DP= 7.06 sq inches
3.5 inch DP= 9.62 sq inches
4 inch DP= 12.56 sq inches

my twin DPs mate in a Burns Stainless Y at the midpipe (Borla 3 inch 40944) and into a RB single. obviously there is give up there but i am willing to make the tradeoff so as not to talk the the guys in blue.


Air Temp is located in the pipe before the elbow and BEFORE the methanol. actually after a run the upper intake manifold is very cold to the touch.... i like that.

split is 11 degrees. i run a J&S Knock Sensor and Retard. it is the later model that includes a MAP sensor so it only activates in boost. it is set to retard IGL up to 10 degrees on knock so, since it does not retard IGT i need to run more than 10 split so as to not have my IGL firing behind my IGT.

since this tuning thread is about AI the duty cycle is interesting...

i made 409 hp on pump gas at 7000 rpm w a 80% injector duty cycle.

i made 410 hp on pump and alcohol at 6050 w a 47% duty cycle, the rest being alcohol. (two M10 1250 CC/Min jets and 850/1600 injectors)

that's a 41% duty cycle reduction due to alcohol and my FJO Peak and Hold injector convertor.

after talking w Jose LeDuc monday i will be running IGL at 10 degrees when i raise the boost to 25 psi. it is one thing to have a bit of knock at one bar and fatal at over 20 psi.... so you start very conservative w re to timing at that level even w alcohol. he should know. he has run 7.63 w his 100% meth 2000 pound 2 rotor RX3.


PEAK HORSEPOWER 425


PEAK TORQUE 353

 

Hows the spool?

 

you actually will loser power mid to top end... a dual 2.75-3" to 3.5" will suffice and weigh lighter than true dual exhaust setups.

 

nice numbers bet you cant wait till aug 5th.

 

sunday aug 19 is the date. and yes i am excited...

hc