Savington

iTrader: (31)

It isn't a particularly hard engine to build, we've just done several of them and know how to set each one up to match the application.

shlammed

iTrader: (8)

currently the engine is still stock and i havent used the 2871R on the 1.8 yet .... just the 1.6

but i loved it then so im sure i will not be dissapointed with the new displacement.

EO2K

iTrader: (37)

...and that is experience I'm willing to pay for. I have no problem learning how to do things for myself, but I also learned a long time ago that there are some things I should just pay to have done by people who know what the hell they are doing.

stinkycheezmonky

If you've rebuilt other motors and gearboxes, I would think you'd be fine to do a car motor. The principles are the same, just keep everything clean and measure tolerances properly.

I did a garage rebuild of two Honda motors, one with a re-bore and one with just a hone. Both lasted 3+ years of tracking and street abuse, no loss of compression or power. Wouldn't hesitate to do it again, and I don't see anything significantly different about a Miata motor that would change that.

vw_nut

iTrader: (1)

I agree with the above. If you can deal with splitting motorcycle engine cases a car engine will seem simple to you.

Landrew

iTrader: (2)

Thanks for the vote of confidence, now to see if I really save that much over Trackspeeds motor. After reading how it is spec'd out, that's a tall order.

sjmarcy

Air cooled 911 engines are cool to work on…just saying...

Landrew

iTrader: (2)

Probably better than replacing the rear spark plugs on a chevy Venture. Ever go caving and turn your lights off and try to move around........

k24madness

iTrader: (6)

I have yet to see any FI pistons for the Miata that impress me. The rest of the available components seem good. I don't know why the pistons technology is lagging behind the rest. I assume it due to the low demand for a good FI piston.

I will likely have a set custom made by CP pistons. They seem to have the best combination of features and quality control.

On a FI specific piston things like extra thick upper ring lands and detonation rings are a must IMHO. X forged, MIL lightening and proper barreling finish out the specs.

spd579

iTrader: (1)

Random question but seems like a good place to drop it. What can the 99-00 non-VVT engines rev to safely? are they different from the VVT's in that aspect?

spd579

iTrader: (1)

anyone?

EO2K

iTrader: (37)

Let us know when you find out

Are you talking a stock or a built motor? I believe the factory set the redline on the stock motor for a reason, not sure how much there is to gain by raising the redline without other breathing mods and ecu mapping to take advantage of it.

spd579

iTrader: (1)

I wouldnt like to rev for more power, I'd like to be able to rev if needed to go deeper into a corner without having to shift. Just wondering what/if there were any differences in the two engines in that aspect. I'll be running AEM EMS with a very overbuilt engine with factory cams. Choke on your moms ****

EO2K

iTrader: (37)

ouch But seriously, you didn't mention anything about your motor or application, so I had to assume.

If the motor is built for it, I wouldn't worry about it. From what I have read, the cam harmonic valve flattening thing only applies to the VVT cams, plenty of folks running higher redlines on built non-VVT BP motors with stock cams. Lots of autoX guys do this with an ECU reflash for specifically the reason you state. PM Sav, he sounds like he has some solid info.

Savington

iTrader: (31)

I wouldn't twist a 99-00 motor past about 7600 if you expect it to last at all. If you want to get more than a couple of years of track use from it, limit revs to 7200-7400.

NiklasFalk

iTrader: (1)

Finally I found a thread that deals with my topic, Valve train design on a built VVT head

I dropped a valve after just four sprint races using stock spring/retainers/keepers/springs with MS SUB and Supertec +1mm valves. The retainer split in half after what I guess was float. The revs was not that high but I was at 7200 for longer periods and a short burst to maybe 7400 when the valve dropped.
This is N/A by the way.

My builder was a bit reluctant to use the stock springs since they are soft, but we were going to continue the build after these four races anyway (if it just had hold together 7 more laps...).

I have tried to read up all that's available on designing a Race valve-train/cam for a VVT system but there isn't much to be found (data/tips on what to do differently).
One comment I found was that too much spring pressure can affect the ability for the VVT to reach the target advance/retard.
Does anyone know what the "holding power" of the VVT is (i.e. would the ability to reach target advance be destroyed by having 50% higher spring load)?

The JDM VVTs have a stock rev limit of 7500 (indicated at least) so the resonance problem cannot be due to the core design, it must be possible to affect with lobe design/springs.

Would a lobe design for a 270-280 cam need to be very different (e.g. much less aggressive landing) than for a non VVT cam ?
Would it be wise to have a hard spring installed with a low pretension, or the other way around (in relation to a fixed cam system)?

I'm shooting for a 7.5-8k engine using forged rods and 12:1 CR (84mm pistons, supplier not chosen yet). The head flow and valves supports 10-10.2mm lift.

It would be bad if part of the resonance is due to the VVT not controlling the cam well enough ("flips" to even more advance when the spring load decreases after max lift), but I hope not. If so it would be worse with stiffer springs.

damir130

There have been some uk people experimenting with JDM RS-roadsters. They found that the only thing revving higher on JDM VVT engines is the tacho. The rev limit is set at the same RPM.
They also found negligible differences in acceleration when compared to bog stock EUDM NBFLs.

Where are you having your cams ground? I'm also looking around. 900$ for a single maruha vvt cam is a bit steep.

Savington

iTrader: (31)

Pretty sure you're on your own for race cam lobe design with VVT motors. The guys to talk to would have been Integral but they've been out of business for more than a year now.

Someday I'll get around to it, but it won't be a naturally aspirated setup.

NiklasFalk

iTrader: (1)

I bought the last VVT cam blank from MazdaSpeed through MiataRoadster for $125.

Hopefully there will be a new supplier for the VVT blanks when I want to try another design (or I have to weld on the stock cam, but cast blanks is a much better option).

Finding firms that grind cams is not a problem, knowing what to desire is a bit trickier.

miata2fast

iTrader: (2)

Generally I do not recommend running stock springs with +1 mm valves. You add a little weight to the valvetrain that way. However with the lighter SUB's I would have thought that you would be OK.

If you want a spring that is a little stiffer, you may consider the earlier 1.8 valve springs. The NB heads used a lighter lifter than the NA, so they used a lighter spring to make more power.