21 replies to this topic

[Jamz14]

This past off season I built a 99. On low fuel loads the car would cutout on left hand corners. The problem getting worse as the fuel load dropped. At the first race I replaced the fuel pump with an aftermarket pump bought from the local parts store. It didn't solve the problem. The fitment into the fuel pump tree was also quite bad. I found a vacuum leak on the car and thought I had fixed the problem, but I found myself at another race with it doing it again. This time I changed the entire fuel pump bracket and pump with a used one that I found at the track. That did not fix the problem either.

 

After talking with people and researching it a bit more, the fuel pump bracket was still coming up as the most likely cause. Because I had replaced the entire thing with a used one, I was hopeful but reserved in thinking that a new one would fix the problem. What were the odds that two were bad in the same way? Turns out the odds were very good. I replaced it with a new one and also found a loose ground. I disconnected the ground completely and tested the car in the garage to see if it would start without the ground. It did. I didn't want to change multiple things in the garage as I like to know what was causing the problem. So I replaced the fuel tree and prepped to replace a number of other items at the track if that turned out not to be the issue. Went friday to a test day and the car ran perfectly. So instead of having to work on the car at the track, I was able to turn it into a good practice day with the new driver in the car. She whipped out 50-60 laps never putting a wheel wrong.

 

I really want to thank Jim Drago, Dave Wheeler, and Mark Nichols for their help in discussing this with me. The joint knowledge base these 3 people have is vast, and their kindness in helping guys like me is equally large. Thank you again.

 

On a side subject: I now have a bit of experience with a 97 NA 1.8, and 99 NB. I drive the 97 and I rent out the 99. There will be weekends where I have a choice of driving either car. Maybe its because I haven't quite dialed in the 99 yet, but there is no doubt that I would choose the 97 as the car I would want to drive in a race. The car is more nimble, lighter, and a higher rev limit than the 99. It is also easier to work on with less complications as the 99, but still has the 1.8 motor and OBDII. Maybe I will change my mind after more experience. But if there were no other considerations ( and there are ), Id choose to build another 97 instead of a 99. Out west there are a few of us that are beginning to think that the NA 1.8 in the hands of a young driver is a better choice.

[Mark]

Don't think so... a higher rev limit than the 99. I'll bet your tach is off in the 97 (no data right?). IIRC the 97 is limited to 6950 or thereabouts.

[Jamz14]

I don't have RPM data logged in the 97 but I think the rev limit on a 97 is 7200. And yes the OEM tach is way off. I think it shows 7600 or so.

[Mark]

Did they change it from the limit on the 94-95 MY?

[Jamz14]

Not sure. I placed a call to mazdaspeed. Didn't know but they are looking into it. Anybody else know the rev limits on the different model years?

 

It sure sounded by ear though that the 97 is spinning higher than the 99. The 99 hitting the limiter caught me off guard the first few times it hit. Data logging shows the 99 at 6800-6900 limit.

[JRHille]

99 should be 7050

[ChrisA]

99 should be 7050

Isn't it 7250...?

[chris haldeman]

99's are all around 6850 on my rollers

[Jim Drago]

Isn't it 7250...?

mine dies right at 7000 mark on dyno jet.

[ChrisA]

Interesting, I thought I had read somewhere that the 99's redline was 7200 officially, but memory may have it confused with another car. I looked at my dyno pulls and some have dropped right at 7000 others around the 68-6900 range. On track my needle goes to about 7100 before spark cuts.

[Jamz14]

Could all these variances be with the ECU?

[Jim Drago]

Could all these variances be with the ECU?

No.

IMO, the difference is most dynos don't deal with the waste spark that well and don,t read it that accurately. I pick up RPM with an electric eye reading a piece of reflective tape on the balancer,  It is correct all the time, never varies. I have heard stories of one well known member searching for a mythical better 99 computer with highest rev limiter because most were 100-150 rpm light. That was not and is not the case. They are all exactly the same, or at least the hundred or so I have tested, they just need to be tested correctly.    

[Erik Hardy]

My Na1.8 is in the 69XXrpm range and the 1.6 is like 71XX, Ish. 

[Brandon]

Confirmed my NA1.8 is 6950 across 3 different ECUs with a dynapak.

[chris haldeman]

This has caused me too go back and look also. I stand corrected 6950 is the number for 99's. I was wrong and Drago was right :-)
I am also using a break beam eye with reflective tape. I have tried multiple pick up methods and this is by far the best

[davew]

We also use the reflective tape on the balancer for RPM pickup. 99-00 are definately 69xx, 1.6's are 7200 IIRC and NA1.8's are +/- 7000

 

ALL TACHS ARE WRONG!!!! I have seen oem tachs as much as 500 rpm high (shows 7700 at a real 7200) and rarely do they read low. At some time, everyone should put the car on the rev limiter in second gear and note what the tach reads. Subtract 300 rpm and that should be very close to the prefered shift point.

 

Dave

[ChrisA]

I just install a shift light in the car this past weekend and need to set the start/finish sequence points. The LEDs are kind of bright, so I thought I'd keep the range tight, so I don't see spots   on the days I need to run the clear visor. I was thinking of starting at 6k and flashing at 68-7k (according to tack). Any thoughts on what is most prefered?

[Jamz14]

Thank you all for the rev limit info.

[Ron Alan]

Well, funny how there is really no clear consensus here. Been awhile since I've seen this come up...and when it has i'm sure i can go back and find(and have always used) what Jim has said. 

 

NA1.6....+/- 7200

NA1.8....+/-6900

NB1.8....+/-7000

 

Never use a stock tach other than your own in car reference if you use it.

 

Side by side my 95 hits rev limiter before any other car other than another NA1.8 car. One of the main complaints/parity issues since the diff ratio rule changed has been the lower rev limiter in the NA1.8(being a small disadvantage at certain tracks)

[Jamz14]

Thanks Ron,

 

Weird, I'd swear that the 99 is limiting out before my NA1.8 . Maybe the engines just sound a little different and it is throwing me off.

 

Thanks Again all and.......... I'd still take my 97 over the 99.