What will happen if i keep driving a 13bt s4 with bad compression to one rotor? Just curios as i have no other daily driver.

 

Do you know whether you have bad compression on just one rotor face (side seal) or on two rotor faces (apex seal)?

You may be able to continue driving for quite some time with no problems other than low power—but if it's an apex seal, that would make me a bit more nervous than a side seal (or just low compression overall). I certainly wouldn't run at high RPMs for very long if that's the case.

What part of Houston are you in?

 

I live in spring off 45north right before the woodlands U?

 

West Side—Highway 6 & Westheimer area.

I daily drive my 'Vert, so I know what it's like not being able to take it out of commission for very long.

I recommend buying a 2nd engine, and rebuilding that...

(Seriously. I have a spare tranny—goes in next weekend. My spare engine should be ready to go in some time next Spring.)

 

any suggestions on where i can get a good rebuild kit? And would you mind looking at my 7 to make sure i aint damaging it worse by daily driving? I planned on taking it to the 7 meet on tuesday and seeing if anyone would help.

 

Are we talking something like 60 PSI all around on 1 rotor, or 0 PSI on 1 or more faces? Running the car with just overall low compression will be a lot more driveable than trying to limp around with 1-2 dead faces. You're probably going to be a major road hazard if it takes you 20 seconds to reach 30 mph.

I have to agree that buying a second motor to prep ahead of time will be the best option since you seem to need to keep the car running for as long as possible. Swapping out short blocks can be done in a day or 2 if you know what you're doing and have at least 1 person to help. Look into getting a used NA motor and then either having it rebuilt professionally or attempting it yourself if you feel up to it. Expect to spend $1k-$3k depending on what you choose.

 

Thanks for the info... stupid question but i thought there was a difference in a na short block and a turbo short block. I have already done some research on some short blocks in my area. Does having an engine overheating and blowing that way cause damage that cant be fixed by a rebuild? i ask because i can get a motor for $200 from someone but the engine overheats and i dont know what kind of internal damage was caused. Thanks again for all the info guys. Also my 7 only starts missing when i apply mid to high throttle under load. i can still get it up to 100 without any problems it just takes a while to get there ( but then i keep hearing that is nothing unusual for the rotories). I can get 0 to 60 in about 12 seconds without causing the engine to miss.

 

the na and turbo short blocks ARE quite different just to clarify

 

Only thing that is similar is the stat gears and e-shaft. Everything is completly different.

 

so i should buy a turbo short block and rebuild that?

 

I would

 

PM Japan2LA. He sells good running motors.

 

hopefully you dont spit a seal through your turbo. time to stop driving it.

 

the housing and rotor are probably already trash...but im guessing the friction could cause seizure and actual breaking of the rotor housing if you really kept pushing it.

 

If you're planning on buying a blown turbo motor to rebuild, try to get one that has had an oil control ring fail. It will have the least chance of internal damage, since low compression motors can send an apex seal through the turbo after gouging a housing. Motors that had a coolant seal fail could have seized up and cracked the water jacked or just rusted everything in place if the owner didn't thoroughly soak the internals with oil.

However, if you do choose to turbo swap, I'd suggest finding a running long block (jspec or otherwise) to rebuild. Then do a ton of research ahead of time to figure out what you have to change to make the swap work. I'll give you one big tip: use the NA engine management (EM) harness, not a TII harness.

 

History on the car was i bought it for way too much and the guy told me it has a j-spec engine and tranny. The vin on the car says it was originally na but is now a turbo II. I do not know which harness it is using. Is there a way i can tell the difference with the harness? I havent been able to confirm. I took it to maz-max here in houston and brian told me that the guys there wont touch it because it has had too many hands in it and is a complete mess under the hood. I see "Rotory Performance" out of dallas/ftw area stickers in the engine bay so i planned on calling them and getting the history of the vehicle. My old boss and friend (owns auto shop for 20 years) says it sounds like lack of spark causing misfire but he is not sure because he said he doesnt know rotaries. I cant even get a compression test run on it because i cant find anyone who will. I did the poor mans compression test and it doesnt seem like bad compression (but then i am new to rotaries). I have already replaced spark plugs and wires and am going to test the coils today. I just don't want to buy and rebuild an engine if it aint a compression issue. Sorry for the long post. I was going to drive it to the houston meet this tuesday and see if i could recruit some help but the car is stuck at a gas station and wont run ( i am getting it towed today). It starts and holds idle but as soon as i put it in gear it floods itself and dies with what feels/sounds like no spark. And to top it all off I have rent due this week and no car for work. I still feel that it will so be worth it if i can get this car going. I always wanted it and i will be damned if i let this make me think bad about my car! Sorry for the long post it is like a vent session.

 

How'd you go from "slow to 100" to "dead at a gas station?" What happened? Folks will need specifics to give you any guidance.

Dont worry about the harness. If it worked when you bought it then it doesnt matter if they acquired a Tii harness or reused the NA harness (which is what we did and what most people seem to do). Either way, you'll want to follow Aaron's procedures to clean up your grounds. Old cars means corrosion and bad grounds confuse the computer.

When you get the car, I'd do a couple of things:

Do a poor man's compression check again. You're looking for two things for each rotor. First, you want 3 consistent pulses. Boom-boom-boom not Boom-bump-bump or Boom-Boom-bump. To test the pulses you need to hold down the little relief valve near the gauge but you need to be consistent in how far you push it or the readings will vary depending on the style of the valve on your particular gauge. Because of the variability of the gauges I frankly dont think the exact number that pops up during the pulses matters (I could vary mine from 0-115 depending on how hard I pushed). And be sure to take out the plugs from the other rotor while doing the test and remove the EGI fuse so you dont get spark or fuel during the test.

Then stop holding the valve and let the pressure build up for a couple of rotations. You'll find it will climb and stop. Record that number and report back. So you should be able to come back and tell us something like:

Rotor 1:
Boom-Boom-Boom 95psi
Rotor 2:
Boom-Boom-Boom 85psi

Folks can make good recommendations with specifics.

 

btw, given that you're worried about making rent, I suggest not even thinking about getting and rebuilding another engine until you've proven this one is truly terminal. You'd be looking at several hundred just in gaskets and seals on top of whatever the short block costs you.

 

Thanks for the info... i will do the compression test first thing after work tomorrow and get back.

 

Ok... did the compression test. dont know if i did it right let me explain. Took off both upper spark plugs and put compressor gauge (snap-on brand) into rotor 1. i did not understand about holding in the relief valve so i just let it go. Will that cause a bad reading. it would hold then jump up some more, hold then jump up some more until it topped out at 75psi. did the same to the 2nd rotor and it went up to 89psi. i am also not sure if i had the engine warm enough because i was in a rush before rain started hitting. Will that also affect the reading from the gauge? Sorry so dumb at this stuff. first time working on engines myself and on top of that a rotary. Thanks for all the help.

On a side note the reason it was towed was it ran out of gas go figure. but it will start and run again. I also did a ignition coil test and all four coils are firing strong. Also if it will help whenever the car is at high revs and i let off the gas to switch gears or just decelerate it shoots fire (which is normal i guess, i have no cats) but i shoot a huge amount of white smoke also. And it only happens at around 6500-7500rpms. just trying to give more info. tomorrow i will try and take a video to make things even easier.

 

Alright just did a compression test while the engine was hot.

Rotor1: boom, boom, boom 75psi
Rotor2: boom, boom, boom 87psi

so i believe i am in need of a motor. is there anywhere i can buy a used one already rebuilt? or do i have to get a used one and then rebuild it?