zoom-zoom-rx7

well the motor is from japan and since it is the cosmo motor it has bigger prots so the guy i talked to said since it has bigger ports the compression will be lower so 90 is good on all faces. Who i got the car from said that the motor had about 35,000 miles on it? oh and when i drove it untuned it was running like 3 psi on the boost gauge but the vacuum line on the external waste gate came off so i drove it twice not hooked up and thought that caused it to not run anymore? i hooked it up and checked the injectors cuz steve kan looked at it and said the primary injectors weren't workin so i rewired everything and the injectors work but it still wont start?

illusionzx

damn, i can't believe you still didn't get a compression test done.

GoodfellaFD3S

iTrader: (213)

Sounds like you've got a mess on your hands, good luck with it.

Oh, and whoever told you that the size of the port runners affects compression needs a spanking 90 psi is not good on all faces.

DaveW

He said ports, not port runners...

I thought that larger (longer?) ports would affect compression the way same that a high-overlap cam would lower compression on a piston engine.

Is this wrong? If so, why?

Dave

Love my RX7

Does anyone have a hood prop for a 93? and a drivers side door handle?

GoodfellaFD3S

iTrader: (213)

Based on what I've seen, compression on a rotary is largely unaffected by porting, at least when you're comparing stock ports to a streetport. Vacuum definitely will be affected of course. No matter how you look at it, saying '90 psi is good compression' is silly, especially when you're trying to sell a motor to someone.

GoodfellaFD3S

iTrader: (213)

Ray Crowe, Malloy Mazda, 888 533 3400.

Love my RX7

How much $?

My email is tylerpohlman@gmail.com or pokerpohlman@hotmail.com

Mahjik

iTrader: (1)

Pick up the phone, call Ray at Malloy Mazda and ask him how much. It's a toll free number.

DaveW

Doesn't the fact that vacuum is lower mean that less air is pulled into the engine to be compressed, and wouldn't that automatically result in at least a bit lower compression? Or is the condition of the apex seals so over-riding that the minor lowering of compression due to porting becomes very small by comparison, and you can't really detect it?

Dave

Mahjik

iTrader: (1)

The rotor would have to be modified to effect compression results. Basically its testing the seal of holding air in the space from the rotor to the housing. So, if there is a break (i.e. apex seal), then it cannot seal as well thus lower compression. Porting doesn't really come into play there as there is a finite amount of space unless the sides of the space are altered (i.e. the rotor).

DaveW

Yes, I understand all that. What I was questioning was that you are basically measuring the compression ratio based on the volume at the time of port closure, to the time of minimum volume in the chamber, minus leakage past any seals, etc. So if the port were not closed off until later, the volume at the time of port closure would be smaller, and the resulting effective compression ratio would be lower, resulting in lower peak compression pressure.

So, that is why I posed this question.

Dave

Love my RX7

Ok. finally got a chance to do a compression test. it was a steady... psh...psh...psh... no gaps or pauses in between.

But... it did spit out gas and air. when i took the plugs out. (they were brand new and the car has only been driven a total of 5-10 blocks with the new plugs) the plugs smelled really gasy. the bottem right one was fairly oily.

after we did that and it spit excess gas out of the plug holes. we then put them back in and tried to start it. it started and ran rough but it did eventually start. would not stay running unless a kept on the gas pedal and above about 1500-2500 RPM's.

drove around the block a couple times and then pulled it around back into the other garage. a lot of smoke was coming out of the muffler. and also there was smoke that was coming out of the hood.

when we popped the hood it seemed to be coming from the turbos. we couldnt tell for sure but we took the filters of the turbos and it kind of looked like there was smoke coming out of the top one. it smelled sorta like burnt oil.

the whole time everything smelled fairly gasy. seems as if the car is getting too much gas. Fuel Regulator maybe?

checked the MAP sensor. hoses appear fine. but i took the MAP off and may try and get a new one. is there a way to test it before i buy a new one? $275 for a brand new one

GoodfellaFD3S

iTrader: (213)

Don't buy a new map sensor. Hell, I'll sell you a good used one I have for 50 bucks....

Love my RX7

yeah... they are going for about 20-40 on ebay for a decent used one. theres no way in hell ill pay 275...