10 replies to this topic

[Rutger]

I have a professionally rebuilt 1.6 that I just acquired in a 1990. I don't know how the previous owner treated it, but it appears to have some problems. I'll summarize the facts, and hopefully you guys can offer some advise.

Problem:
- weak low rpm pull, improves as rpm above 4,000
- sounds like valve float or strange lifter sounds above 5,000 rpm and on deceleration after high rev above 6,000 rpm
- puff of white smoke (doesn't look like water vapor) on startup and faintly on deceleration from high rpm
- plugs have black carbon on the body of the plug and brown/black on electrode area
- black carbon inside the tailpipe
- exhaust smells exceptionally rich/oily

Checks:

- doesn't leak any oil, oil level seams stable
- compression is stable at 220 - 225 across all 4 cylinders

I have not done a leakdown as The compression is high.

Thanks in advance.

[Ron Alan]

"Weak low rpm pull" LOL...welcome to a Miata! Put it in another gear...should never be much below 5k on track. Not an engine guy but wish we had 220 compression! Our motor always quiets down after a oil change and always blows smoke on start up w/stock lower end and new head. But i was told this would happen...NP.

[Rutger]

Thanks for the comment. I have heard that something to be done is have the computer reprogrammed to raise the rev limiter? What rpm does the stock rev limiter kick in at? My gauges redline at 8,000 but I have not taken it to redline yet. I normally shift at 6,500 - max 7k.

"Weak low rpm pull" LOL...welcome to a Miata! Put it in another gear...should never be much below 5k on track. Not an engine guy but wish we had 220 compression! Our motor always quiets down after a oil change and always blows smoke on start up w/stock lower end and new head. But i was told this would happen...NP.

[Jim Boemler]

Several of your questions indicate that you haven't grasped the rules yet. Your car has a rev limiter at about 7200 RPM, and the rules require it to stay there. Unless you find a line in the rules that says you can change something, you have to leave it alone.

[Tom Hampton]

Thanks for the comment. I have heard that something to be done is have the computer reprogrammed to raise the rev limiter? What rpm does the stock rev limiter kick in at? My gauges redline at 8,000 but I have not taken it to redline yet. I normally shift at 6,500 - max 7k.

Rutger-

What class are you planning on racing in? You need a rulebook. SM does not allow modification of the ECU. We prefer for everyone to buy 6 (10 or 200) ECUs and dyno them all to find the magic ECU. For some other class that allows ECU mod/replacement (IT?) you would probably be better off changing the computer entirely.

Stock redline is around 7200-7400 rpm (it varies from ECU to ECU). Get it up there...you should know what it sounds/feels like before you experience it on the track. Put it in first or second, and drive down the street until you hit the limit (at legal speeds, of course!). You won't hurt anything. Its often better to bang the rev limiter for a moment than short shift (or lug the engine) when you are approaching a braking zone. Also, get a secondary tach...the stock tach can have its own errors. Mine reads about 200 rpm (a tick mark) low at redline compared to my G2X.

[Tom Hampton]

Several of your questions indicate that you haven't grasped the rules yet. Your car has a rev limiter at about 7200 RPM, and the rules require it to stay there. Unless you find a line in the rules that says you can change something, you have to leave it alone.

Oh, come on....there's another way! Get a large portion of the class to start doing it, and then get it added to the rules...because the horse is out of the barn. <ducking flying tomato>

[Jim Boemler]

I think you might be confusing Rutger without the history, Tom.

Apologies if you're running only ITA, Rutger -- my comment assumed you were going to be in SM. Which you should, BTW. SM is where you'll find close competition, where you can hone your skills. Most folks use ITA as a way to race twice as much in a weekend, but ITA races are a rather scattered thing. SM is the place to be.

[Rutger]

Thanks Jim,

I suppose I should clarify.

I have an ITA compliant car that is NOT Spec Miata compliant. I want to work towards getting the car SM compliant, so I can race that class in the future but this is adding cost I cant bear today (buying a new crate motor, new compliant exhaust, 4 corners of coils and shocks, ditching the willwood brake system, etc, etc,) as I retroactively remove the IT stuff and convert it to spec.

In the meantime I will be racing IT only, and I have some questions relating to what I can do currently, as well as future.

Therefore, my posts may seem like I am schizophrenic, but I am not.

I have a copy of the SCCA regs and my local clubs supplemental GCR's. I totally "get" the "if it does not specifically say you can, you can't", hoever there is still vagueness in some areas, such as the ignition system section covers carbuerated models just fine, but doesn't really cover details on FI.

If you can't tell, I am a novice, so I have spent a lot of time lurking the board, searching historical posts, and surfing through the old specmiata.com site. Now the rubber hits the road with questions I have not been able to answer.


Thanks!

I think you might be confusing Rutger without the history, Tom.

Apologies if you're running only ITA, Rutger -- my comment assumed you were going to be in SM. Which you should, BTW. SM is where you'll find close competition, where you can hone your skills. Most folks use ITA as a way to race twice as much in a weekend, but ITA races are a rather scattered thing. SM is the place to be.

[Tom Hampton]

I think you might be confusing Rutger without the history, Tom.

I know. But, I guess I'm feeling frisky today. Besides, he says he's read the old site....time for some lessons!

We still need some better emoticons. You'd think the new JD would get that fixed!

-tch

[Jim Boemler]

We still need some better emoticons. You'd think the new JD would get that fixed!

Yeah, the old "dead horse" emoticon is still needed. There are a few goodies on specmiataclassifieds.com that could be useful as well.

Thanks for describing your situation better, Rutger. I obviously think you're on the right track moving towards SM, but I wonder if converting this car is the way to do it. Somebody out there may still like the idea of IT-only, or may be moving towards FP instead. For that person, your existing build may have some value. For your (SM) purposes, what you've got is little more than a stock donor. What I'm thinking is that you may be better off selling your car and buying an "already-SM" car instead. Hassle, I agree, but maybe worth considering.

[dstevens]

There is a normal clatter and a not so normal clatter on the HLAs (lifters) I haven't learned the difference but I can say that I just tore down a 93 longnose with 80k miles and it looked good, except for the 7 bad HLAs. Take them out and if you can squeeze them with your fingers and have it move then they are shot. Then I dropped the eighth one and knocked the button out of the center. Parts Dinosaur has the Kia OEM with the same part number.

You guys looking for a dead horse emoticon...

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