peejay

Drove it in to work yesterday, with TunerStudio (an utterly shitty program but it's the only option) doing an "autotune" that I will have to go in and unfuck later.

Believe it or not, it has a whole lot less mid range torque than a bridge port has.



Have some wiring issues still to sort out, but so far, it's not sucking coolant, which is a plus. Cannot get the idle below 1500rpm, which is a minus.

rotarygod

iTrader: (1)

That intake manifold has huge runners and is really only good for top end power so I believe it.

peejay

Drove it around a bit more today (about 2mi) after replacing the semi worn heat range 10 plugs with a set of new FC trailing plugs. I know that it's moving less air at WOT since the VE tables are about 20% lower at atmospheric, so I doubt I'm going to be running into plug overheating issues like I had been with the bridge port. Plus our courses tend to have much shorter straights, so I really should have done this regardless.

The 10s are cheaper as well, however I don't know if it's the heat range, or the gap, or the fact that they are single strap plugs, but they did not tolerate mixtures even close to stoich. I know I can run a stockport on FC plugs at around 15-16:1 cruise.

My left knee also really appreciates being able to cruise in gear instead of havign to shift in and out of gear every few seconds. I might be able to live with this instead of swapping in an automatic. (Or I might swap an automatic into the '81, who knows)


The midrange is better than I was expecting, to be honest. Part of it may be that you need to open the throttle more on an engine that isn't constantly on the verge of being at WOT

60 miles on the engine. Have only burnt 3 gallons of fuel, even with a bunch of idling and running way beyond pig rich. Not bad, not bad. Can't wait to tune it further on Saturday.

peejay

Engine has about 1200mi on it now, almost half of that done this weekend.

I haven't gone to a dyno but I have done some 2nd gear pulls while towing a trailer, and it is somewhat interesting in that it doesn't feel like torque peaks.

What I mean is, with any of my old stock-manifold street ports, the powerband would kick in like a switch at about 5500 and it would taper off at or after 8000rpm. With the bridge ports, they sort of woke up around 2000rpm and hauled all the *** from there on out. This engine's torque curve is a crescendo. It just keeps pulling harder the higher you rev it. I have been having tach bouncing issues but I am fairly sure that I've had it up to over 9000 (ahem) and it always had a definite sensation that the higher you revved it the more torque it made.

That's not terribly good for a performance engine, if you don't have a CVT.

peejay

The muffler fell off about 20mi before getting to the event. Racing Beat pipes get paper thin after twenty years. RB shows the rear muffler as still being backordered, Mazdatrix had one in stock, it's ordered and on the way.

Mostly I am getting around the power issue by not lifting as much. I also made some changes to the front end geometry that mean I don't have to lift as much, either;

j9fd3s

iTrader: (3)

[QUOTE=peejay;12348599and it is somewhat interesting in that it doesn't feel like torque peaks.
[/QUOTE]

it actually sounds like its a decent combination. i wonder if it wants a longer intake runner?

peejay

Probably does. It's not going to get one, mind you. I had to cut some of the hood reinforcement out for air cleaner clearance. Whatever brand Holley manifold this is, is maybe an inch taller than Racing Beat.

It'd be interesting to try a wrapover DCOE manifold but I can't think of one that isn't also somewhat restrictive.

I DO have that Lake Cities style manifold. If I stuck a 50mm throttle body on it and made up the runner length with trumpets, that might be interesting.

Kenku

... I have been looking for an excuse to cast my lake cities style manifold that goes to 50mm snowmobile ITBs...

j9fd3s

iTrader: (3)

i tried one on a stock 12A and was really surprised at the low end it had. it really came on around 2000rpm, and was kind of flat by 6, its using a 45 dcoe, so carb is on the small side

j9fd3s

iTrader: (3)

oh and of course we missed the most important part, the geometry change worked?

peejay

I am pleased with it. Was able to lower the front 30mm and also get good turn in. I found a geometry calculator tool and it looked like it actually reduced bumpsteer, although I didn't bother to measure actual.

If anything the rear needs more grip now.

peejay

Minor update. Spent the last month with the car laid up due to a broken U joint and used the time to do some other upgrades. Went back out and proceeded to wreck the 9" again. Destroyed the pinion bearings.

On course I find myself frequently at around 5000rpm in 2nd gear (4.44 gear, 62cm tires) which is suboptimal when the engine doesn't pull down there. I will probably send my bridge ported bits to Chips for resurfacing and go back to bridge.

j9fd3s

iTrader: (3)

whats up with that? maybe you can find a way to use the Ford housing and the Mazda diff?

peejay

It'd be nice.. although I also am using 31 spline axles, which I think are physically larger than the ID of the Mazda carrier bearings.

Turn it up and enable closed captioning.

peejay

If it looks like my forearm muscles are bulging, I now have a 2:1 quickener on top of a depowered 3 port FC rack. It works out to about 1.3 turns lock to lock... no assist... Feels really good actually, I can actually feel what the front tires are doing now, but it takes a bit of muscle.

diabolical1

iTrader: (3)

looks like a lot of fun, Peejay. how many years have you been doing Rally?

j9fd3s

iTrader: (3)

my friend bought a Lancia Scorpion, and its a great car to drive, because it really makes you drive it. there are a couple of surprising things about that car, but the steering rack is really quick, it feels great, and since the engine isn't on it, its really light too. the other thing is that it only looks good when its moving, when its parked nobody cares, but as soon as its moving, it might as well be a naked lady with a plate of sandwiches or something.

the down side of the Scorpion is that they spent about $14 developing it, and it shows. the other problem is that the engine is behind you it has this two step turn in, one where you turn the wheel and it does what you want, and 2 where it wants to just keep rotating. i have a feeling that if you break traction with it, its going to be very exciting....

peejay

diabolocal, technically I haven't been doing it at all I guess technical-technically I did four or five TSDs about a decade-plus ago, sometimes with rallycross friends and sometimes with a fellow FB owner (Jon Bartels, IIRC he went by "nevarmore" on the forums) I could drive like a robot and he could do time-based math very well so it was a lot of fun. Getting shot at by the locals in Lower Methopotamia for driving on "their" roads was less fun.

But I've been doing rallycross since 2004... it's kind of weird since that was right around when the SCCA started doing it officially, so i'm kind of one of the old farts in the discipline. That and being a tech-minded rules lawyer is probably why they stuck me on the national rules committee and I tend to get to be on the protest committee at national level events I get to hit.

One more video:


The problem didn't really exist after my over-winter front suspension tweaks (new struts, stiffer springs, raised roll center) butit came back.... after I adjusted my struts to full soft after my second run. I made that adjustment trying to soak up some of the rough stuff better. Before second heat, I re-adjusted the struts to their baseline setting and the problem went back to mostly non-existent.



I wish I could figure out how to copy/paste photos. In the process of buying photos from one of the on-site photographers but I don't feel like waiting until that is done before I posted this video. What I could see from those photos is that the suspension is going to full compression and then just sort of staying there. The binding is probably the tire grinding on the inner fender structure - at max compression there is room for a 195/60 street tire, not a chunky 185/65 gravel tire.



So my current plan is to try to acquire another subframe and modify it for an even more radical roll center change, which will require alteration beyond merely redrilling holes. I'd also like to try some 250lb springs if I find any for sale cheap. Really, it'd probably be easiest to yank out the FC subframe and re-install FB parts, but then I'd need to find a steering box that I could splice a quickener into and frankly I don't feel like doing that right now. Finding another subframe to modify is easier.

peejay

Pic from the event.



Suspension does do a good job of lifting the inside front on corner exits. Weight transfer is actually a good thing on dirt if you're not trying to power that axle. If both wheels were on the ground, the steering is less responsive because there's less bite. But you have to be going fast enough to have enough grip to go fast.

diabolical1

iTrader: (3)

i am ashamed of myself for misspeaking, and as someone that likes to watch rally races whenever i can find them, i should be.

so you're 15 years in. that's massive cool! i've been an SCCA member since the late 90s and have yet to run an event ... in anything! so you definitely have my respect and admiration.

as far as the car goes, (if i get what you're saying) you're trying to raise it a little more? at least, that's what my neanderthal brain saw/read, and i guess it makes sense for your discipline. it's actually pretty weird (but in a cool way) to see an Rx-7 pick up a front wheel.


all i can say to this is ... what the what???

peejay

I'm trying to raise the front roll center so I can get the front lower. I'd also like to get the rear lower, too. I'm thinking that I need tires with more grip in order to get as much cornering with a lower CG.

When it's lower, it runs a lot cooler on the highway. That's my main concern there. As it is the temps stay at about 110 degrees over ambient with a floor of 170F. (So on a 90 degree day the coolant temps are 200)

Southeast Ohio is full of clannish folk. SE Ohio is also where are the really fun roads are since it's the foothills of the Appalachian range.. C&D used to test their cars there. The people around the Hocking Hills area are pretty nice (they get a lot of money from tourism after all - lots of cool vacation spots and historical sites to visit), but there are some folk elsewhere that basically don't like outsiders.

They weren't too bad about it, you know, but still brandishing rifles and shooting over your car as you drive by is kind of an indicator that you're not welcome.

peejay

My old long-travel suspension (Subaru WRX rear struts, modified to suit, with 175lb springs) baaarely lifting a wheel:

peejay

hkp

iTrader: (2)

what throttle body are you using?

peejay

None, it's a carburetor with a TPS on it.