Black1993rx7

I recently took my 1993 Rx7 touring to AIM Tuning in Indianapolis. I wanted to get the car checked out before I bought it. Everything is in good running order but the compression seems to be a bit low. I believe the compression should be around 8, but the front rotor had 5.8, 5.7, and 5.9. and the rear rotor 5.3, 5.3, 5.5. I was wondering if there's anything that can be done to fix the ratio. Forgive me as I’m very new to the rotary world and I've done research already.

Eventually I’m looking at an ls swap when the 13b dies but I’d like to keep it running as long as possible. I'm going to put a down pipe and a cat-back on just to help the heat in the engine bay but that's all I plan to do with the 13b. If anyone has any ideas for the compression I’d appreciate it.

BobfisH

rebuild the engine unfortunately is the only choice.

sounds liek youd better put an LS in it sooner than anticipated.

Monkman33

iTrader: (28)

If you rebuild before something breaks, it can end up saving you some money. And it sounds like you are getting on the lower end of acceptable compression.

AnthonyNYC

iTrader: (3)

You need to know the cranking speed as well. The lower the cranking speed, the lower the reading. On the back of the Mazda compression tester has a chart that shows the relation between cranking speed and compression readings. If I remember correctly, they can be as low as mid 4s with the lowest cranking speed.

Anthony

mdpalmer

iTrader: (24)

Also, make sure that the gas pedal is held down during the test. Some have reported lower numbers if they didn't do this

round 1: https://www.rx7club.com/showthread.p...ht=compression
round 2: https://www.rx7club.com/showthread.p...ht=compression

Even experienced people can make mistakes

c00lduke

Also, the engine temp can change your numbers. The manual suggest the engine being warm at the time of the test.

Rocking Rotary

iTrader: (14)

There are many valid points here.

Make sure you have a good charge on the battery when you test. I do not test mine with the throttle open or the engine warm and I yeild good numbers on good engines and poor numbers on blown engines. Test when its warm only masks problems the same with opening the throttle plates to get that extra air in the housings. Blown is blown no matter which way you look at it.

You should have a hard time starting that car cold. If so the compression results were right on. If I was in your shoes I would pull the engine for a rebuild it will be least costly in the long run. Plus you dont want to have a apex seal fail and then you need to buy a rotor housing and rotor at least.

If your on a bugget or want a quality build use Rotary Resurrection he comes highly recommended!

GoodfellaFD3S

iTrader: (213)

Black1993rx7

thank you all for your courteous responses. As far as I can tell a rebuild is simply replacing gaskets, seals, o rings and springs. I found a kit on eBay (link below) and was wondering if this kit is enough to fix the problem. Again, I just want to keep the 13b in good running order until next year when the LS goes in.

http://cgi.ebay.com/ebaymotors/Maste...spagenameZWD1V

The testing RPM was 253 and 250 for the front and rear respectively. I’m not sure if it was done with the throttle open or not but the guy who did it is extremely qualified (supposedly). Also, the battery is brand new so that shouldn’t be an issue. In response to Rockin Rotary, the car starts promptly with no hesitation at all. Its unfortunate that rotaries are so unreliable… I love the power and response I get out of a 1.3L; however I don’t have the money to constantly rebuild.

dgeesaman

iTrader: (7)

There is a thread stickied at the top of this forum that contains the Factory Service Manual. Download that and check out page C-9 for details and a chart that shows how to adjust for RPM. 250 is right in the middle of that range, so I think it's safe to say you need a rebuild pretty soon.

Engines like this don't need constantly rebuilt if you run them near stock power and keep up with the basic maintenance. Stock engines usually last over 75k - while that's not quite a smallblock Ford engine, it's hardly what I'd call 'constant'. The more power you go for, the shorter the average lifespan becomes.

Dave