bill Shurvinton

Holley compared to dellorto or injection is not that impressive. At 6000 RPm its over 20HP down on the dellorto. Doesn't equal it until 7200. Peak figure is good, but won't be anywhere near as fast on the road.

Kim

But basicly you can use ANY proper sized TB on a custom intake manifold along with either the stock TPS or an aftermarket one?

bill Shurvinton

Basically yes, but you'll have you use an aftermarket fuel computer

Kim

OR

Kim

The apexi afc seems like a cheap/nice product But whereas the haltech controls everything, the apexi only controls fuel Yes?

bill Shurvinton

There are a number of options as well as those, from the build it yourself up to motec. If you can't stand soldering then the perfect power/microtech/wolf are all good starting points.

It also depends whether you like fit and forget or you like to forever tinker and optimise.

Bill

Kim

Fit and forget please
My seven is driven everyday so it just HAS to work, I dont mind soldering, I do it on a daily basis so that aint stopping me.
So far this thread has helped me alot. I have allready plans in my head how it is gonna look like.

whats the wolf website? I cant seem to find it

bill Shurvinton

www.wolfems.com.au

Kim

thanks

pengarufoo

I have the TWM setup on my car with a E6K controlling fuel and ignition, on a street port self built motor (new). I just started the car for the first time this week and have it starting and idling pretty nicely, no load tuning will begin shortly.

Kim, if you decide to go this route, there are a number of things required to be fabricated, and it gets pricey fast. Feel free to email me if you have any questions.

Kim

Thanks Pengarufoo, but the forum(mother) says that you have chosen not to recive e-mails through the forum, I tried other people and it was the same.

Anyways I still dont know what the "TWM" means, or how it looks.
I think a few pics. would do me good so that I can see if im on the right path.

So far my idea is to keep the LIM and make a custom equallength UIM with some throttlebodies and the stock TPS.

Im fully capable of fabricating the entire setup my self, so dont hold your thoughts on this project but do remember that im gonna drive this car everyday to and from work.

pengarufoo

you can email me at
swivel at pengaru.com

TWM is a manufacturer of these ITB configurations. www.twminduction.com

I have plenty of pictures which can probably be of use.

mazdized

I am having a Holley manifold on the way. I am running a Holley double pumper and racing beat header out to single 2 1/2 inch exhaust. I will let you know what I got. With the exhaust now it is dynoing 143 hp at the wheel.

mazdized

Oh. on my bridge it dynoed 220 at the wheels. I had street port with identical set up, but I never dynoed that, it feels about 190-200 at wheel. I am hoping 160-170 at the wheel with the Holley and factory six port 180k minles motor. Holley's fuel ecomnomy is hard o beat except FI.

OC_

iv worked with FI so much over the years it would be hard for me to put a carb on my engine, i would much rather shell out the cash and get a stand alone computer. The plenum setup with internal velocity stacks is the way to go for me. I could probably fab the entire thing, but theres things i dont know. i wouldnt know how long to make the runners to make power at 'X' rpm, and i dont know how big i would make the plenum. Theres a lot of after market throttle bodys around, so im sure there would be one that would work great for us. all i can really do is guess. i guess that we would be working with pretty short runners because we are trying to tune for high R power. if i could could get some info/suggestions about runner length and plenum size and so on, i think i could do some damage!

bill Shurvinton

Plenum design for the rotaries is a somewhat unpublished black art. To be honest they work so well in an individual runner set up I'm not sure that there is a lot of advantage anyway, as you just add throttle lag.

There are lots of notes around on how to calculate runner lengths though. Rotarygod published a spreadsheet which I haven't checked but looks fully in the ball park. The tircky bit is deciding what you actually want from your engine, as the RB article clearly shows the effect that you can shunt the torque curve around quite a bit, with significant changes to the HO curve ensuing.

As for TBs, as you can fab things up. I would score a set of TBs off a GSXR750 or 1000. These are tapered bodies, 48 in 40mm out and come with all the gubbins (map, TPS, fuel rail etc) for around $60-80 on ebay. They are spaced almost perfectly for a 13B and would provide a near perfect air feed. If you rip out the horrid port actuators you should be hitting 240 at the flywheel. The actual max for the street port if you put peak torque at 8000 would be 260, but that would be nasty to drive unless you did a slidey trumpet.

Bill

rotarygod

iTrader: (1)

Actually the spreadsheet wasn't posted by me. I found errors in it. The formula was posted by me though and it gets you extremely close. All of my calculations after measuring Mazda factory manifolds and comparing them to published specs has always given me results which predicts less than 1/4" error at the greatest with the actual product but usually much closer along the lines of a tenth or so. Close enough. Temperature and altitude will effect it more than that.

Remember that an engine designed to be shifted at 8500 rpm is useless if you have the stock gear ratio transmission which is designed to be shifted at 7000 rpm. The fastest cars will be designed around a total package which takes rpm limits and gear ratios into account. For a stock 2nd gen tranny you should set your peak power goal somewhere around 7000 rpm. If you are going to custom fab an upper manifold, design it in a way that the runners are equal length. The front runner is 1" longer than the rear which sets the power peak for each rotor at slightly different rpms. The rear runner needs to be longer. No aftermarket upper manifold accounts for this. If you really want to get trick, find a way to taper the size of the runners down by 1 degree over the entire length of the runner. This is optimal. Even if you do the individual runner thing I still recommend a plenum BEFORE the throttlebodies. There is a benefit that you can get from Helmholtz resonant tuning. If you build the manifold and want some info on how to design the plenum PM me and I'll help you out. You can tune any style port to almost any rpm if you do it properly. Good luck.

bill Shurvinton

Sorry, misappropriation there.

I don't understand your assertions on transmission ratios there. OK on a stock box 1st is way too short, but the key is the power curve such that you drop back onto it when you shift rather than falling off the bottom. So the shift RPM doesn't matter as long as the package is right and you can do this with a stock box. Unless I have missed something in the translation (limey here)

Last time I tried to calculate a helmoholtz resonator for a 13B it came out with a design that would either cause a major restriction at high RPM or was so enourmous that it really didn't make a lot of odds so would be interested in seeing your numbers on that.

rotarygod

iTrader: (1)

A shift point on a stock transmission between 7000-8000rpm will be fine. Basically I am referring to people who want some crazy 10000 rpm shift point but don't have the gear ratios to support it. The stock transmission is designed around a very wide powerband with a relatively low (in relation to a race car) shift point. When an engine is tuned for a higher power peak then the powerband also narrows. Optimally the gear ratio should be changed to account for this. Guru Racing has a great transmission that is designed around a 9500 rpm shift point. The ratios are close enough that when you shift, the engine rpm's only fall to 6500 rpm. This keeps more radical engines in their powerband. An engine designed for this use would mate up terribly with the stock tranny. You get the point. The key is to not get too carried away. If this is primarily a streetcar then I don't think he'll have a problem. It is more a less some advice in case someone comes in and foolishly says to rev it up sky high.

As far as the Helmholtz plenum thing goes, I like to start with a plenum size on a 13B of around 200 cu. in. in volume. The intake tube size is determined by the desired peak power rpm's airflow potential. The max air velocity at peak power rpm should not exceed 122.83 mph. I don't recall the math formula off the top of my head. I'm tired and sitting in the middle of a hurricane right now. Anyways, after these two things are made I just adjust the length on a dyno until it corresponds with the desired power peak. This must be adjusted with the air filter on the end of the tube since the air filter changes the flow characteristics slightly. If the desired power peak is at 8000 rpm basically start at about 6.5" in length and adjust from there. It is very easy to fab up a small interchangeable system that can be adjusted on the spot.

bill Shurvinton

I did some sums based on a 50DCOE TB and reckoned that 200CI is too small, as you won't have 2R clearance aound the trumpet, which may cause some unwanted reflections. If you have a 45 you'll be OK though. (NB I need to check that I haven't gotten that assertion wrong).

Helmholtz is f=c/2Pi.(sqrt(A/L.V)).

So if L=15cm and V is 4000cc and A is about 25cm2

gives 102 Hz, which should give peaks at around 4000 and 8000 RPM ( for best filling tune for f at twice piston filling rate.) So it could be argued that we need to up the frequency a bit there. However this is the point where theory means little and dynos give results. But I'd guess nearer 12" for a 6000 RPM peak fill.

I'm interested in this as I need to fab an airbox for my car to fit the upper injectors so have rechecking my sums on the todo list, Too many times I've seen an airbox cause a smooth curve to go lumpy and loose 5-10% power.

But seems last time I did the sums wrong.

Cheers

Bill

OC_

so... what would be more cost effective? building a custom intake mani and so on, or just getting a turbo engine? it seems that if your going to build a custom FI intake manifold, it would cost about the same for a much more streetable turbo engine. Since you would need a stand alone ECM for the custom setup....

Kim

OMG all the techtalk really got me thinking twice about this, but offcourse I need more power its just a matter of how its done (Turbo or N/A)

bill Shurvinton

Addendum. I was looking at the filling frequency wrongly, you have 2 rotors so at 6000RPM the filling frequency will be 200Hz, so 'theory' says you tune for 400. However I suspect that 200 will still be helpful.

Multiplex

Hey Everyone,

Kim I hope you don't mind I'm gonne try and add some info to your wonderfull thread.

First of, interesting this all is, I am new to performance tuning rotaries (or engines in general) so many stuff above here I only understand a little of.

Just like Kim I also have a 6 port NA engine I want to get some more performance out of, I'm not yet at the stage where porting becomes interesting but I want to dive into the subject and get as many info about it as I can.

So here are a couple of novice questions to which I can't find answers to (or the given answers I did not recognise because I am a novice), so hope someone would be willing to explain these.

First, looking at the auxilary ports on the 6 port. If I compare it with a streetported sidehousing for a 4 port it strikes me that the total area of the 2 ports on the 6 port isn't that much different, if not bigger then the streetported 4port. So why would I not want to stick with the 6 port setup and just make the ports bigger on the center housing? It seems that the valve has a positive effect on lower end torgue (while the side housing change will have a slightly negative effect).

Second, why is it that making the ports bigger has such negative effect on low end torgue? Is it because when the engine rotates slowly the bigger air ducts make it harder to pull in the air, or has it got to do with the overlap with the exhaust and compression stroke?

Hope someone can explain some of the basics for me so that a novice like me can get a bit further in understanding tuning a rotary

bill Shurvinton

You are correct in that it would be nice to get port areas closer to the same, but there is a problem with the centre housings that limits port size. I haven't ground one out myself so I'm going on slight conjecture here but ISTR that the EGR passages are very close to the port, so to get a 'big' centre port requires you to devcon all that up. Doable, but not necessarily good for high reliability.

As to port size and torque, its all about velocity. Air velocity is what helps make torque. Big runners and low RPM =poor velocity and no torque. No free lunch here, but that is why you have 3 different modes of operation in the 6-port

1. primaries only
2. primaries and secondaries
3. As 2 with Aux port