It's baaaack...
04-05-08, 08:01 PM
#2
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things that go brap in the night, alex?
04-07-08, 09:47 PM
#7
Old [Sch|F]ool
Thread Starter
Because it is. 
I think I see where the lawn mower comments come from... that's not a lawnmower blade, that's a sunroof front flappy thing from the '79-only sunroof.
I think I see where the lawn mower comments come from... that's not a lawnmower blade, that's a sunroof front flappy thing from the '79-only sunroof.
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04-09-08, 12:52 AM
#11
What are the goals for the car? I plan on building a homebrew PP over the next couple summers off from school. I read youre write up on your web page and I gotta say I love the enginuity. I have a summer job at a CNC and fab shop for sprint cars and competition pulling tractors, so I think I should have the tools necessary to build something similar 
What are some of the things youd do different if you built a PP from scratch, again?
What are some of the things youd do different if you built a PP from scratch, again?
04-09-08, 11:45 AM
#13
Old [Sch|F]ool
Thread Starter
My goals are torque in the 3k-6k range without a turbo.
Actually, those were my goals when I built it in '05. I still believe those are valid goals, but right now it's just a case of running out of engines to put into the car, so it's this or nothing
I much prefer running hard in 2nd instead of soft in 1st because it's so much easier on the cooling system, and the spate of engine losses I have had since switching to rally tires seems to suggest that slip/stick at high RPM is bad for the engines.
If this doesn't meet my goals, I'm probably going to talk to Palpatine and join the Dark Side, with a manual-shifted automatic and a Series II Buick 3800. I *know* that will do exactly what I need from the car.
sorry for teh huge
Actually, those were my goals when I built it in '05. I still believe those are valid goals, but right now it's just a case of running out of engines to put into the car, so it's this or nothing
I much prefer running hard in 2nd instead of soft in 1st because it's so much easier on the cooling system, and the spate of engine losses I have had since switching to rally tires seems to suggest that slip/stick at high RPM is bad for the engines.
If this doesn't meet my goals, I'm probably going to talk to Palpatine and join the Dark Side, with a manual-shifted automatic and a Series II Buick 3800. I *know* that will do exactly what I need from the car.
sorry for teh huge
04-09-08, 04:37 PM
#15
Old [Sch|F]ool
Thread Starter
That was why I went with 14" runners. The SAE papers suggested that was a good length. Unfortunately, cramming 14" runners and a Holley under the hood made the manifold less than stellar which was contributing to my problems.
Current manifold is going to be a 2x40mm throttle body and the runners will be (get this...) u-bends sourced from the muffler of a Boxster. Porsche parts on the Mazda. Hopefully it doesn't depreciate the car too much
Current manifold is going to be a 2x40mm throttle body and the runners will be (get this...) u-bends sourced from the muffler of a Boxster. Porsche parts on the Mazda. Hopefully it doesn't depreciate the car too much
04-09-08, 06:28 PM
#16
Arent 40mm a bit small? Thats just a hair over 1 1/2" and didnt you use 1 3/4" sleaves? The muffler piping sounds resourceful! Good to hear youre not going with the Holley lol. I could really figure out how that thing would have gotten descent atomization an velocity. The show I work for makes ITB setups for sprint car V8s in tons of sizes. I dont think theyve ever made them for a rotary, but Im sure I could find a couple spares and slap on. What are using as an EMS? I cant wait to see the build once it gets started!
04-09-08, 07:19 PM
#17
Old [Sch|F]ool
Thread Starter
Actually, my *runners* are also 40mm ID, give or take. Besides, as mentioned before, I don't *care* about the top end. Top end is useless for me, and really, good top end is detrimental. One of the things that makes my VW so easy to drive is that I don't have to let off when the tires spin. The power band dies at 5200 and there's over 1000rpm of cushion before the hard limiter, so I can just lay in on it until the car speed catches up.
This is of course without a nice close ratio gearset. With the stockport 12As (after peejay-tweaking) I would get rancid tire spin in 1st gear and shift up at 7k-8k or so and then the engine would bog back down to 3k and go nowhere. It'd be nice to make more torque down low and taper off as RPM goes up - more of a flat power curve than a flat torque curve.
If I was going to do it over again, I would have run thick wall aluminum tube and run it all the way through and then made my port shape to suit. (There is a build in the single turbo section that is how I *really* would have done it, if I had those kind of resources) And I would have done an FC 13B since the housings are usually in much better shape, and they come with 2mm seals and better rotor gears.
This is of course without a nice close ratio gearset. With the stockport 12As (after peejay-tweaking) I would get rancid tire spin in 1st gear and shift up at 7k-8k or so and then the engine would bog back down to 3k and go nowhere. It'd be nice to make more torque down low and taper off as RPM goes up - more of a flat power curve than a flat torque curve.
If I was going to do it over again, I would have run thick wall aluminum tube and run it all the way through and then made my port shape to suit. (There is a build in the single turbo section that is how I *really* would have done it, if I had those kind of resources) And I would have done an FC 13B since the housings are usually in much better shape, and they come with 2mm seals and better rotor gears.
04-09-08, 10:12 PM
#19
Old [Sch|F]ool
Thread Starter
I don't rally, I rallycross. BIG difference.
A lot of our competitors are students at Purdue. And they go to rallycrosses in Columbus and Detroit, not just Dayton...
If I was rallying, I'd have a good gearbox. What's a couple thousand on top of the $10k+ it takes to build the rest of the car? Homebuilt P-ports are not uncommon in US rally.
A lot of our competitors are students at Purdue. And they go to rallycrosses in Columbus and Detroit, not just Dayton...
If I was rallying, I'd have a good gearbox. What's a couple thousand on top of the $10k+ it takes to build the rest of the car?
Homebuilt P-ports are not uncommon in US rally.
04-10-08, 11:31 AM
#23
Old [Sch|F]ool
Thread Starter
Okay, now that I have time to elucidate.
The problem isn't the rearend gears, the problem is the *transmission* gears. The drops are way too large.
Even with something as bogus as a stockport, when the tires would start spinning in 1st, the revs would climb right up to max safe levels and beyond unless you let off. That makes it very hard to drive when you don't have time to look at the gauges, let alone concentrate on keeping the engine alive. So an engine that makes good power at 6000-8000ish would need max revs around 11k or so in order to be drivable. Upshift at 8k with tirespin with the stock gearsets (have used one each of 1st-gen transmission types as well as a S5 N/A) and the revs drop down to 3k, which while still somewhat useful is a BIG drop in HP and the car goes nowhere.
So the goal, then, without running *super* low gears (4.78s would still have been too tall, think something in the low 6's would have been about right) and a T10 or an RX-8 trans (ignore 1st gear), or super low gears and a *really* bucks-up Quaife gearset, is simply to bring the powerband down so there is a healthy RPM cushion up top, and when (not if, *when*) the revs get bogged down after an upshift, the engine still has some oomph down there and maybe it doesn't bog so bad.
Also, I have found that running at 6-8k for a minute-plus in 1st gear, with short trips to second, causes big time overheating. The stock water pumps suck, and there isn't enough room for a decent radiator. Keeping revs down allows the water pump to pump water instead of making vapor bubbles.
So I can spend $5-7k on better gearing, and still have cooling system problems, or I can spend a couple hundred bucks and make a peripheral port. My power goals are only in the 150hp range, more than that is useless.
The problem isn't the rearend gears, the problem is the *transmission* gears. The drops are way too large.
Even with something as bogus as a stockport, when the tires would start spinning in 1st, the revs would climb right up to max safe levels and beyond unless you let off. That makes it very hard to drive when you don't have time to look at the gauges, let alone concentrate on keeping the engine alive. So an engine that makes good power at 6000-8000ish would need max revs around 11k or so in order to be drivable. Upshift at 8k with tirespin with the stock gearsets (have used one each of 1st-gen transmission types as well as a S5 N/A) and the revs drop down to 3k, which while still somewhat useful is a BIG drop in HP and the car goes nowhere.
So the goal, then, without running *super* low gears (4.78s would still have been too tall, think something in the low 6's would have been about right) and a T10 or an RX-8 trans (ignore 1st gear), or super low gears and a *really* bucks-up Quaife gearset, is simply to bring the powerband down so there is a healthy RPM cushion up top, and when (not if, *when*) the revs get bogged down after an upshift, the engine still has some oomph down there and maybe it doesn't bog so bad.
Also, I have found that running at 6-8k for a minute-plus in 1st gear, with short trips to second, causes big time overheating.
The stock water pumps suck, and there isn't enough room for a decent radiator. Keeping revs down allows the water pump to pump water instead of making vapor bubbles.So I can spend $5-7k on better gearing, and still have cooling system problems, or I can spend a couple hundred bucks and make a peripheral port. My power goals are only in the 150hp range, more than that is useless.
04-10-08, 02:58 PM
#24
That that I see your power goal, everything makes a lot more sense. I guess I kind of forgot that too much power would make for a particularly useless car in the dirt. As for your cooling problems, Have you thought about buying a universal alum radiator similar to what stock car guys use? Afco makes a sweet little 2.5" dual pass in a 22,24,26,and28x19" and run around $200. I suppose a large majority of the over heating is due to insufficient air flow at low speeds, but a amp hog of an electric fan like the Taurus fan could also help that quite a bit. Have you looked at a miata gear set? Although the first 3 gears are actually higher, the ratios are closer together.
04-10-08, 04:53 PM
#25
Old [Sch|F]ool
Thread Starter
Miata gears are too expensive.
See my build thread on ohiorotaries.com as far as my cooling system trials and tribulations. Will post the pics here tomorrow - GTG!
See my build thread on ohiorotaries.com as far as my cooling system trials and tribulations.
Will post the pics here tomorrow - GTG!