Cal Club Autocross Forums

... money. Only cost something like $65 including shipping on eBay. Told me my O2 sensors were OK, and that it's the first CAT that needs to be replaced. Thanks MazdaSpeed for knocking $200 off of the price of that CAT.

I further noticed in the "live" reading mode that the timing advance varies from under 10 degrees advance to over 40. I thought on these older cars, '99 Miata, that the timing didn't change? If you're in a class that allows one to advance the timing ... does that advance the "starting" timing value? Say you advance your timing 5 degrees ... would all of my readings be 5 degrees further advanced?

I guess our '99 Miata can't take advantage of higher octane because it doesn't have a knock sensor to aggressively advance timing when it has higher octane available? Even my '97 Previa can do that.

Mako Koiwai wrote:... does that advance the "starting" timing value? Say you advance your timing 5 degrees ... would all of my readings be 5 degrees further advanced?

Yup.

Mako Koiwai wrote:... money. Only cost something like $65 including shipping on eBay. Told me my O2 sensors were OK, and that it's the first CAT that needs to be replaced. Thanks MazdaSpeed for knocking $200 off of the price of that CAT.

I further noticed in the "live" reading mode that the timing advance varies from under 10 degrees advance to over 40. I thought on these older cars, '99 Miata, that the timing didn't change? If you're in a class that allows one to advance the timing ... does that advance the "starting" timing value? Say you advance your timing 5 degrees ... would all of my readings be 5 degrees further advanced?

I guess our '99 Miata can't take advantage of higher octane because it doesn't have a knock sensor to aggressively advance timing when it has higher octane available? Even my '97 Previa can do that.

You can't reset the timing on an OBDII car, and more important, it's a waste of time on the Miata. The Previa engine was built to run on premium. The knock sensor is there to protect the engine when using lower octane fuel. The Miata runs on regular, so no knock-sensor.

Previa was designed to run on lower octane fuel, but it says it will offer better performance with higher grade fuels. It's surprisingly noticeable.

Select Octane Rating 87 or higher. For improved vehicle performance, the use of a premium unleaded gasoline of 91 octane or higher is recommended.

In all my years of owning a Previa I didn't know that. How noticeable is it?

You probably DO notice how you lose power on a hot day ... the 91 makes up for that, at least on the SuperCharged model. I sometimes think it gets better mileage on 91, ie. more power, less throttle for the same speed = a wash on cost.

Let's line them up!

As long as Mako's isn't the SC model, I'm game.

Tom Tanquary wrote:As long as Mako's isn't the SC model, I'm game.

Chaces are good that it would make less power due to losses in the squealing supercharger bearing!

Mako Koiwai wrote:...I guess our '99 Miata can't take advantage of higher octane because it doesn't have a knock sensor t...

Then it sure seems like something's wrong, as my 10AE came w/a knock sensor!

Sitting on the shifter is not a knock sensor.

Mako Koiwai wrote:Previa was designed to run on lower octane fuel, but it says it will offer better performance with higher grade fuels. It's surprisingly noticeable.

Select Octane Rating 87 or higher. For improved vehicle performance, the use of a premium unleaded gasoline of 91 octane or higher is recommended.

The Previa was designed to run on on premium and used the knock sensor and ECU to run on regular. Horsepower and torque ratings were derived from tests using premium fuel. The owner's manual quote is not a statement regarding how the vehicle was engineered.

Bill Schenker wrote:

Mako Koiwai wrote:...I guess our '99 Miata can't take advantage of higher octane because it doesn't have a knock sensor t...

Then it sure seems like something's wrong, as my 10AE came w/a knock sensor!

I take that back. However, the Miata from 90-2004 was designed to run on regular.

Mako Koiwai wrote:... money. Only cost something like $65 including shipping on eBay. Told me my O2 sensors were OK, and that it's the first CAT that needs to be replaced. Thanks MazdaSpeed for knocking $200 off of the price of that CAT.

I further noticed in the "live" reading mode that the timing advance varies from under 10 degrees advance to over 40. I thought on these older cars, '99 Miata, that the timing didn't change? If you're in a class that allows one to advance the timing ... does that advance the "starting" timing value? Say you advance your timing 5 degrees ... would all of my readings be 5 degrees further advanced?

I guess our '99 Miata can't take advantage of higher octane because it doesn't have a knock sensor to aggressively advance timing when it has higher octane available? Even my '97 Previa can do that.

i was looking up obd2 scanners on ebay. there are multiple ones available. do you mind specifying which one you purchased?

thanks

Bob Beamesderfer wrote:

Bill Schenker wrote:

Mako Koiwai wrote:...I guess our '99 Miata can't take advantage of higher octane because it doesn't have a knock sensor t...

Then it sure seems like something's wrong, as my 10AE came w/a knock sensor!

I take that back. However, the Miata from 90-2004 was designed to run on regular.

My 01 has 'Premium Recommended' both on the gas flap and in the owners manual. With the VVT my understanding is it will retard the timing if you use regular... I haven't tried.

2001-2005 Miatas love premium fuel.

Leonard Cachola wrote:2001-2005 Miatas love premium fuel.

'99 is tuned for 87 ... anything more is a waste. It won't take advantage of higher octane, unlike WRX's/STI's.

2001 has higher compression, thus 91 octane.

Mike ... my eBay special:

http://cgi.ebay.com/ebaymotors/ws/eBayI ... &viewitem=

The green one.

When my battery went flat, it told me when it was OK to get it smogged, ie. when enough cycles had been run through the ECU for it to pass.

Earlier I used it to verify that my O2 sensors were OK and that the first CAT needed to be replaced.

We used it last weekend on Henry's misfiring Vette ... to see that there were no error codes, etc.

When you get error codes you go on-line to see what it is. 100's of codes ... many very specific. There are general codes and then manufacturer specific codes.

I would like to get a OBDII code reader to check my car, so looking for recomandations.

The ebay link no longer valid, what brand/model do you have?

Bill Schenker wrote:

Mako Koiwai wrote:...I guess our '99 Miata can't take advantage of higher octane because it doesn't have a knock sensor t...

Then it sure seems like something's wrong, as my 10AE came w/a knock sensor!

I was going to say the same thing. I know the 99 has a knock sensor. I know this because we hooked it up to the new AEM ECU. I'm very familure with every sensor in the car now.

Once upon a time I owned a '90 Miata.....and kept meticulous records of my gas mileage for years (in hind sight, I wonder why I did it ... anyway I did) ... tried various fuels and found that the best power/gas mileage was using Midgrade....then Premium (which was barely better than regular...but worse mileage than Midgrade) and lastly regular, for which it was rated.

Advancing the timing gave a bit more torque down low and didn't seem to hurt the top end revs ... others even advanced the timing on the intake cam for better power (moved it ahead one tooth on the timing belt) ... Info can be found on the Miata.net on those ...

So, whenever I went to an autocross, I'd make sure it was running midgrade fuel at the vapour level on the gage ...

Reijo

Kristoffer Gjevre wrote:I would like to get a OBDII code reader to check my car, so looking for recomandations.

The ebay link no longer valid, what brand/model do you have?

Kris Cho posted this in another thread: http://www.ultra-gauge.com/ultragauge/index.htm" onclick="window.open(this.href);return false;

OBDII data readouts & checks/resets codes too for only $60! I can't attest to how good it is though...

Kristoffer Gjevre wrote:I would like to get a OBDII code reader to check my car, so looking for recomandations.

The ebay link no longer valid, what brand/model do you have?

Not sure if they still do it, but Pep Boys rents out OBDII readers for free - at least when we needed to check something on my coworker's car about 3-4 years ago.

Of course, it's nice to have your own, but if you only plan on using it a handful of times during a year, why not rent for free?

Actually anyone have an OBDI reader. Don't find them very often, and I don't want to spend the $200 for a reader that is OBDI & OBDII, but would like to read/reset some codes on the Corvette.