I was wondering how many people have done this mod? I have done a search on the forum and found that it only increases performance after 6000rpm. Now i have a 92 dx pros and it redlines around 6200rpm. Now is it really worth the effort? How could you increase redline limit?

 

The RX7 meter really only helps out on high-rpm breathing of the BP DOHC. The peak hp of the engine is at 6500rpm I believe and redlines at 7k rpm. The BP SOHC just doesn't do much at that rpm. Randy has a webpage that details the install and adjustment on 1.8L BP dohc Miata engines and many have done the swap on the BP in the Protege. Is it worth it? No, probably not unless you plan on doing head work, cam regrinds or a head swap. You can increase the redline by using new head and ecu. Again, the sohc doesn't create power at that high rpm anyway. Correct me if necessary.

 

Oh, and try to post engine questions in the right forum the next time.

 

I took the VAF off my RX-7 and put it on my 92 Protege DX with the 1.8L SOHC. It helped that engine tremendously. My SOHC Pro will destroy a DOHC 1.8L, easily. I went to the track with just that mod and I ran 16.6. I could've ran faster times if I had on bigger wheels than the factory 13's. I'm guessing it can run low 16's. If none of you believe me, I will scan some of my timeslips. Maybe this will stop some of the idiots talking crap about the SOHC.

 

Just a question for you - did you take your DX to the track before you put on the VAF (and a cone AF?). Car and Driver tested one in '94 and ran the 1/4 in 16.8 secs, and they are usually a little slower than what can be achieved (they usually don't do big, wheel-spinning clutch drops).

And people don't bag on the 1st-gen DX as much as the 92hp 2nd-gens. I've mentioned several times that the DX is nearly as quick as the LX, especially 0-60, but the top speed is lower due to gearing differences, and on a road course, the close ratios of the LX would be advantageous. It also helps that the DX is about 100 lbs lighter than the LX.

But, since the RX-7 VAF only helps the DOHC LX over 6k rpms, it makes logical sense that it wouldn't help a car whose stock power peak is only 5500 rpms, and whose redline is only 6200 (IIRC).

Now, if you have a dyno plot that shows that it does make a difference on the SOHC DX, I'm sure there are a lot of people who would like to see it. But butt dynos are notoriously inaccurate, which is why your statement would tend to be met with some skepticism.

BTW, their are several 1st-gen LXs here that have run low 16's, some with big, power-robbing wheels and tires.

 

I didn't take my car to the track before the VAF. Also, I launched at idle, otherwise, I would be sitting at the line spinning.

 

You may find that with slicks that you have too much traction for your available HP. I couldn't keep my 15" Azenis spinning at the drag strip, and the car would bog. Of course, that was also at 2710 feet, so YMMV.

I am curious to know how much they help.