sixshooter

iTrader: (12)

Don't get too crazy if you are that close to Rotrex's terminal velocity, haha. It is important to keep things together.

Concentrate on weight, weight, weight.

And if you really want to get particular about maximizing what you've got for high RPMs, you might want to get a little ----. Along with the parts you put on your list I would look closely at streamlining the efficiency of every part you are running. For instance, have you checked the pressure gradient between the inlet and outlet of your intercooler at your peak power? It may provide ample cooling capacity but might still be a flow restriction at the full CFMs the Rotrex is providing. Any tight bends in the inlet tract you could straighten out? A rule of thumb in fluid dynamics is that every 90* bend in a pipe creates as much added drag on what flows through it as a 20 foot long section of the same diameter pipe. So we should look to minimize bends and when necessary we should make them wide and smooth radii. Obviously this would apply to exhaust design as well as pre-supercharger. And use a larger air filter element than you think you need, lol.


BTW, do you have the ATI damper and Boundary OPGs? I hope so at those RPMs.

185km is only about 114mph or so, right? If that's all you are seeing at your power level then that's a very tight track. I'm going to say the 6speed with the 4.10s will be quite a bit more advantageous than the 5 speed in that environment.

18psi

iTrader: (76)

Well obviously, he owns a miata.

sixshooter

iTrader: (12)

Let me help them. A belt driven centrifugal supercharger spins faster as the engine spins faster and continues to push more air into the engine as it increases in RPMs. It does not fall in efficiency and flow like a positive displacement supercharger does and therefore makes dyno graphs that look like laser beam trajectories instead of bottle rocket trajectories, if you get what I mean. The centrifugal looks like a turbo's compressor wheel. It actually does drop off eventually but you will actually have it typically disintegrate from overspeeding first.

sixshooter

iTrader: (12)

I though you'd like that when I wrote it.

18psi

iTrader: (76)

Couldn't have said it better myself.
The kicker is that it won't start blowing hot air like a turbo once its past its rpm limit. You get no warnings.

falcon

iTrader: (13)

Yeah I was thinking about my IC. It's quite small. And the piping is definatley not ideal with all the couplers and bends. I have a Maruha oil pump but stock pulley. ATI is on the list too, just didn't mention it. The oil pump is debatable, I have a feeling it's a modified VVT pump but Ocean my motor builder builds high comp N/A 1.8's that spin to 9k and make 200whp with this pump and has never had a failure.

Yeah 114ish MPH. It's a small track with a short straight away. I mainly built the car for hill climbs though, and the 6spd should help with the light bog out of uphill hairpins I'm having right now.

Watch this vid and you can get what I mean. The red light on the dash is 7800RPM for reference. I am running a 5spd, 13's and a 4.1 in this vid. You can see where the car bogs.

sixshooter

iTrader: (12)

Yeah, :53 and 1:22 and 1:51 it was pretty noticeable.

Big Chinese intercoolers are cheap. I doubt you are running A/C where you are so you should have plenty of room for one.

falcon

iTrader: (13)

Yeah I have a "little" chinese IC right now. I have no PS or AC so yeah I have space. I'll look into it. If I'm going back to the dyno for a 3'' exhaust I'll do the IC too.

Savington

iTrader: (31)

You don't understand how a centrifugal blower works either. Centrifugal blowers build boost with RPM. It has nothing to do with the camshafts.

JasonC SBB

falcon you really need to show us the boost plot, and better yet, calculate and plot torque divided by MAP every 500 RPM. With this plot you can tell what your VE is and where it peaks. You will know if the engine isn't breathing well.

Read this book excerpt of why BMEP is so important, from the book "4 stroke performance tuning" - he talks about n/a motors, and for a boosted motor the equivalent BMEP is BMEP divided by MAP:
http://books.google.com/books?id=OTO...ortant&f=false

Read this too:

https://www.miataturbo.net/engine-performance-56/bmep-divided-map-why-its-important-60527/

miata2fast

iTrader: (2)

I know exactly how a centrifugal blower works. I have one, and have driven many.

I however do not know how a centrifugal is controlled, and have not studied the dyno plots of them and compared them with other induction methods. I assumed that there was a valve that kept it from continuing to build boost.

Also, Falcon said his advertised duration was somewhere close to 300. That is a ******* monster cam. My advertised duration is 237, and I turn my N/A motor 8000 rpm. After looking back did I realize that his @.050 was what he thinks maybe was at no more than 214. So what is it? A giant cam or a ***** cam. I am doing the best I can with the information brought before me.

falcon

iTrader: (13)

Lol, A valve? You say you know how it works, but clearly you don't.

And the overall duration of the cams is 300, .050 is 207* and 213*. .050 and overall duration are not the same thing. you can have a cam with big overall duration and smaller .050. Dosen't make it a "monster cam or a ***** cam". Quite a bit of thought was put into the cam profiles by my motor builder and tuner, and it seems to be doing the job quite well. I doubt I would be making 300whp on stock cams. Sure more torque but not 300whp at 16-17PSI on a 1.6L.




Again... you really have no clue how centerfugal chargers work. Just to be clear.




I'll have to dig around for the boost curve. I'm in Europe right now and don't have access to a lot of car stuff. If I have it on my photobucket I can post it up, I'll go check.

miata2fast

iTrader: (2)

First of all, I was not throwing you under the bus with my statement about the camshaft. Lets be clear on that.

I made some assumptions that you may have a really big cam. You said you were unsure of what you had. I am well aware that advertised duration is measured differently from manufacturer to manufacturer, but you stated that yours was a full 63* bigger than my cam at advertised duration. That is quite a difference.

For the record, I clearly said that I was unfamiliar with the control of centrifugal blowers. I do however have some experience with matching combos together like cylinder head and camshaft selection with proper final drive gear ratios. Let's not make this a pissing contest, thank you. Just trying to help.

Savington

iTrader: (31)

You really don't get it, dude. His torque curve has nothing to do with the camshafts. The nature of the blower produces that torque curve regardless of the cam - I've seen motors with that blower and stock cams make the same curve.

It's clear that you and techsalvager have the same misconception about falcon's cams being so large that the motor never reaches its torque peak within the allowable RPM range, but that's just how a Rotrex works. Smaller cams may help, but we already talked about that a page or two ago, and they won't change the shape of the torque curve - if it has an effect, it will bump the midrange and decrease the top end (probably disproportionately).

I hope you've been here long enough to know that dickwaving your "experience" will not even slightly change our opinion of you.

sixshooter

iTrader: (12)

Advertised duration is measured at .003 lift.

falcon

iTrader: (13)

Ah, yes.. my mistake ^. I was going of memory.



At the end of the day, the cams are staying in. I don't feel like pulling them, re doing shims/swapping lifters etc. for other cams. Before I do any big changes, well... not that there is really anything much left to do other than the exhaust and maybe an IC I am going to get a 6pd and see how that changes the car.

Savington

iTrader: (31)

You'll try it, it will be insufficient to mask the feminist characteristics of your setup, you'll start another thread like this in a year, and eventually you will man up and buy a built VVT/turbo package from TSE.

falcon

iTrader: (13)

Lol... yea prob. Seeing as how much you guys charge for motors it's a really really good deal. I wouldn't mind though, building a VVT Rotrex'd motor.

Until I get some competition that is faster than me, my current set up is enough for now. It's been enough to set a few records so it's no slouch. I really need to learn how to drive the car faster though.

falcon

iTrader: (13)

Lol... yea prob. Seeing as how much you guys charge for motors it's a really really good deal. I wouldn't mind though, building a VVT Rotrex'd motor.

Until I get some competition that is faster than me, my current set up is enough for now. It's been enough to set a few records so it's no slouch. I really need to learn how to drive the car faster though.

JasonC SBB

falcon,

You are not going to gain 10% torque from diddling the exhaust or i/c. Forget it.
Next to the boost curve generated by the centri, the cams have the biggest effect on the shape of the torque curve.