wankelbug

im looking to buy a 13b engine with low miles and the seller claims 180ish compression seems high to me but i have little experience with roto motors. does this number seem exaggerated or un obtainable?

2slow4stock

iTrader: (18)

LOL 180 is a ridiculous number. 120-130 psi = brand new excellent engine. 110-120 psi = still good. 80-90 psi = a little wear still ok, anything under 70psi isn't so good. (you can run and drive it, but could blow any given time it wants. <-- (unless it was rebuilt low miles that isn't broken in.)

wankelbug

it is claimed to have less than 10k on it motor is coming out for a v8 swap. i heard it run, start , rev ect no smoking or rough running or misses from what i could tell. i come from piston engines and kinda freaked when i heard that number but thought maybe theese rotos do those kind of numbers. this engine is coming out of a well taken care of car from someone with a deep pocket. ok for question number 2. if the motor does need a rebuild is $450 too high for a turn key motor with manual trans with all the fuel injection and ecu radiator ect ?

lastphaseofthis

iTrader: (8)

First of all, on most piston engines, 180 would be low, and they run in the 220-240 psi range for new. 180 is a complete lie, or misunderstanding, if he said 108, that would be good and useable. but V8 guys usually have no idea what they are talking about anyway.

pfsantos

iTrader: (1)

Have him do a compression test, video it, and post it, like this guy did:

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/compression-test-good-bad-854166/

Supernaut

iTrader: (83)

This is the way I look at the numbers...

130 = brand new (I believe they came from factory like this)
120-130 = excellent
110-120 = very good
100-110 = good
90-100 = mediocre
80-90 = engine getting tired, start planning for a rebuild
below 80 is bad bad bad

180 is very suspect. Maybe he didnt normalize the results. I dont know. Thats just not right.

wankelbug

he is pulling the motor now. or i would. when i said piston engines i mean aircooled vw 120-135 range is good for those engines.

supernaut what do you mean by normalize the results?

arghx

iTrader: (3)

compression test results must be normalized for the cranking rpm:

wankelbug

well im getting the motor either way ill do a comp test once i get it home. does anyone need the transmission from this? its manual. make me an offer.

misterstyx69

iTrader: (142)

why?..WHY?..why would you get an engine from someone who may be Fudging the Compression Numbers?.
I would be Running away with my Money,to Elsewhere.
Not to Be Disrespectful,but you did ask For Opinion on this,and it looks like you have your mind made up,and are going to get the engine Regardless.
If you do have your Mind Set on this engine,then LOOK UP Compression Test(..try this site : www.rotaryresurrection.com hit tech and look up how to do a Comp check with a piston tester).
Do the Check in front of the guy or have him Show YOU how HE did his compression check,so you get the Numbers.
If the numbers are Low,then Offer him a LOW Dollar amount.(if you Want it Still.)
If they are OK then still Offer him a LOWER amount,than what he is asking,to See if he will Play Ball.
.It is your Money and you can always walk away.Rotary Engines are a Dime a Dozen.this is NOT the only engine around.
Shop around.Good luck to you however you decide.STYX.

wankelbug

well talked to the man selling the engine he was unable to get started on the engine pull today so i jumped at the opportunity under your advise styx and im going by first thing tomorrow to do a compression test. he didn't hesitate to allow me to so id imagine its on the up and up but peace of mind is worth it.

pfsantos

iTrader: (1)

Now you're making sense...

wankelbug

think i was making sense the whole time. im not an idiot. i did hear the motor run start rev ran like a top. just that odd number threw me off.

with the schrader valve removed on my tester while turning the motor will i see the actual operating pressure of the engine? or does it just show weather or not i have a bad chamber on a rotor? i know you do the test with and without the schrader valve installed. so after i let it build pressure that number should be in the 100-130 range correct?

misterstyx69

iTrader: (142)

Cough. http://www.rotaryresurrection.com/2n...ion_check.html and yes..if you let the tester build compression it should hit 100's and Over if it is Decent.

wankelbug

was having problems with that site my computer blows *****.

wankelbug

well i did the test build 120psi removed the valve and it pulsed evenly up to about 80psi so i bought it. just waiting for my brother to get home so we can get this out of the truck.