shlammed

iTrader: (8)

cool, thanks!

Do you mind sending me a copy of your AEM tune for either this rental or your ninty-fo (pre E85) to compare to my current tune? i wouldnt mind checking out some of your settings.
m.moore13@hotmail.com

I have the VVT engine on its way, and not to toot my own horn but i think that i am quite good at wiring.

emilio700

iTrader: (3)

Sav,

You considered trying a VVTuner?

timg

Some folks might consider this off topic, but this thread seems like the best place to have the debate.

I like the idea of a simple / low hp track Miata that is affordable. The '949 rental' method is nice and all but still a good bit of money (unless you needed a new engine anyways for example). How would this method compare to just a real simple low (LOW!) boost turbo setup that made 150 whp with a small turbo with tons of response?

This is assuming one has a decent reasonably low mileage stock pre-99 engine already of course. Cost wise I think one could probably do the turbo cheaper than the engine swap. The programmable ECU is the same for both, exhaust could be the same, clutch, etc.

Basically comparing the cost of the turbo/plumbing/intercooler with the cost of the new VVT engine/cams/etc.

This low boost 140-150whp engine should be pretty darn reliable no?

Is it all about the throttle response? If so, is it really that much 'worse' to justify the extra cost/complexity to do the VVT swap?

Discuss..

Tim

scottyd

This reason for going n/a was reliability. On any given track weekend, the rental will see two drivers going out for 5 sessions over 2 days. That's 20 20 minute sessions of ***** to the wall driving. That's almost 7hrs of racing. This thing has never had an issue.

I love love love turbo cars but reliability goes down and complexity always goes up when a turbo enters the picture.

timg

I agree that the car is dead reliable. I guess I'm wondering if a stock 1.8L @ 150whp and a properly sized 'cheapish' turbo could not also be dead reliable? I'm thinking that Lemons Miata with the junkyard engine turbo that just keeps going and going.. good evidence that a very low boost/low power turbo Miata can be reliable?

I'm not convinced either way, just trying to keep an open mind about it.

Tim

Savington

iTrader: (31)

I'd love to play with one. We ended up with an AEM for this car.

150whp NA looks like this:
-VVT motor, $800
-RB header, $400
-B18 intake manifold, $400
-custom intake, $100
Total: $1700

150whp turbo looks like this:
-Manifold/downpipe, $800
-used/rebuilt SR20 T25 turbo, $250
-Inconel studs, $160 (we did say reliable, after all.)
-intercooler, pipes, and intake, $300
-oil/water lines, $150
-injectors and fuel pump, $250 (cleaned/flowed Rx7s or similar)
Total: $1910

The turbo car will be more likely to cook stuff in the engine bay due to the excess heat, and it will be less of a learning tool. You can take the turbo car and spin the power up a little higher, sure, but we weren't looking for anything more than 140-150whp with this car. If you go beyond that it becomes a much less forgiving car to drive, which makes it much less fun for drivers who are just starting out.

For 200whp, turbo makes sense, but not for only 150whp.

timg

To be fair, you won't make 150 whp with your NA numbers.. don't you need a cam for that? Also, can you really get a VVT for $800?

Stock injectors/fuel pump won't handle 140 whp?

We are splitting hairs here I guess. I guess I'm more wondering how reliable a low boost 150 whp Miata is compared to the VVT engine. I think we can all agree that a bargain hunter can set himself up with a low boost turbo setup for significantly less than the above. The VVT engine setup is more like $1200 minimum. So if the cheaper boost method is 'almost' as reliable.. why not?

Tim

shlammed

iTrader: (8)

almost doesnt cut it when people are paying to drive it.... not to watch you fix it.

and yes, if you know your way around you can get a VVT engine for 800... i just bought one off ebay for 500$

Savington

iTrader: (31)

sigh.

-Yes, we will make 150whp with a VVT motor, intake manifold, IHE, and an ECU. Lots of folks making 130-140whp with '99 motors and stock intake manifolds, and the IM is worth 10-15whp on its own. Emilio made ~160whp with a very similar package - the differences are the head (VVT vs. '99 w/ BP5A and .020 shave) and intake manifold (EUDM Squaretop vs. B18). The VVT head will make the same midrange as the '99 head with a little less top end, which is a fair tradeoff for never having to open the valve cover on this motor.

-Speak for yourself on the bargain hunting. Lots of folks make that claim, but for whatever reason none of them ever show up at the track. Feel free to prove me wrong, but I won't be holding my breath (no offense).

-If the cheaper boost method (which isn't cheaper) is "almost as reliable", why not? Uh, cause it's more expensive and less reliable. Reliability was priority 1, 3, and 4 on this car (safety was 2). I know what it takes to build a reliable turbo track car, and having now built a reliable N/A track car, I can say with a fair bit of confidence that for 150whp, N/A is cheaper.

shlammed

iTrader: (8)

Towards me?

Savington

iTrader: (31)

No, towards timg. I don't mean to insult him, but the "well you can do it way cheaper than that" argument is pretty stale at this point. Lots of people talk the talk, but I haven't seen anyone walk the walk.

redrider706

iTrader: (4)

Hi Savington,

Does the exhaust header (stock or RB) mate to the catalytic converter/test pipe at the stock 90-93 location? If not, what did you do for the exhaust?

emilio700

iTrader: (3)

Just to get full closed loop VVT control. Have to say though, the plots you posted so little overshoot as to make that issue kinda moot. Having a few AEM's laying around, I'm more inclined to run just that on our next VVT project.

Savington

iTrader: (31)

here's that plot for folks that didn't see it on m.net. I literally have like 3 minutes of tune time into the VVT PI settings. This is also revving in neutral and purposely making big jumps to try and confuse the ECU - I'm sure an in-gear log would be much closer.

Savington

iTrader: (31)

It's a 94-97 RB header with EGR plugged, and a 1.6 liter RB cat and exhaust. We lengthened the cat pipe in-house a little bit to meet up with the header.

timg

No worries on insulting me.. it is just a discussion, and I'm educating myself here (as I'm sure you can tell ). The NA recipe does sound pretty attractive if one can find VVT engines that cheap, didn't realize that.

I agree on the bargain hunting.. but there are quality turbo parts for sale in the classified section all the time so it is doable, just seems nobody HAS done it and kept the power down to a reliable level. Boost is addictive I guess and nobody has the restraint to keep it low power.

I'd love to see somebody with a 150 whp turbo beat it on the track and see what happens. Proper studs and decent radiator / coolant reroute should make it pretty reliable no? I guess your point is.. "pretty reliable" isn't good enough and not on the same level as the VVT. I get it.. just can't find VVTs around here (eastern Canada) as easy as that so one looks for other options.

How much power does one cut off the above setup compared to just dropping the 99 head on a 1.8L block? I guess that is a reliable 130whp?

Tim

Jimmy vegas

Another benefit to N/A is the power delivery for novice/rental applications. With a turbo (even a low pressure small turbo) you are managing boost as well as rpm vs the linear delivery of N/A (essentially just managing rpm).

I know I'm a noob here so my .02 might get blasted, but simple(r) is usually better.

ryanmx5

iTrader: (2)

Since you say the tricky part is the wiring for the fuel injectors, would the 94+ models need wiring changes since they are already wired for sequential injection from the factory?

Also, would a different fuel rail (m-tuned) or modifications need done to a '94 with a vvt swap?

Savington

iTrader: (31)

The '94 still needs two of the injectors moved over to the center connector (1 and 2). 3 and 4 can stay in the OEM harness.

Fuel rail depends on which intake manifold you use. For some reason I remember the '01 rail not working for some reason, but the '99 rail does - but the '99 rail fouls the intake manifold a little bit. Whatever you use for an OEM rail, you use the 1.6 FPR in place of the fuel damper.

shlammed

iTrader: (8)

i sent you a PM about asking for a copy of your tune so i can try to get my engine setup with the sensors properly... is that something you would be willing to do, or is this a "tuners dont share tunes" thing.

you can completely erase your spark and fuel... i just would like some aid in setting up the crank angle, cam angle and VVT solinoid settings.

i know there is a VVT setting thread in the aem forum, but it doesnt have the final page and i would still be lacking crank and cam angles