sparkscarz

hey guys i tried searching this but couldn't find anything.
so i got a 87 S4 N/A. got a couple bolt on mods but it feels weak. haven't done a compression test yet but when i crank it with no EGI fuse it kinda sounds like only 1 rotor is making compression.
how do i figure out if im running on 1 rotor?

Hernan1209

iTrader: (4)

Take off the leading spark plug on each rotor, you should hear three shhhh, per revolution of the eccentric shaft, if you har one that means apex seal is gone, if you hear two a side seal is gone. Perform the test on both rotos and if you are running with just one you will hear the difference.

sparkscarz

should preform this test with the EGI fuse in? and i do hear 3 shhhes when i crank but how do i know witch housing it from?

satch

iTrader: (1)

If you pull the lower plug off of the front housing then the swoosh's, if present, would come from that housing and not the other. Same goes for the rear housing. And you can pull either EGI fuse.

sparkscarz

so id need a buddy cranking while i listen right? would the swooshes be a significantly different sound then the rotor trying to start?
also how can i do a compression test on this thing :S

satch

iTrader: (1)

It would help to have an assistant though there is a way around that, but it requires jumpering voltage from the battery to the Black/White wire that leads to the starter solenoid. To do a compression test you would need a device that measures the pressure and this tool can be purchased at most auto supply stores but there needs to be an adjustment made to it to get a more accurate reading that relates to a valve on the gauge. Using the advanced search function will allow you to specifically find out how to do this.

Hernan1209

iTrader: (4)

The easiest and cheap way is to buy a compression tester at you local auto parts, about $30. Used the leading spark plug hole for the test. Take EGI fuse off. With the valve open you should see three jumps of the needle. Close the valve and cranck the engine for 5 seconds, if you have 90 psi of compression in that rotor, seals are good, 80 psi or less you will break at any moment.

wthdidusay82

iTrader: (15)

bro , if its running on 1 rotor it'd be pretty easy to tell, the only way you'll have similar symptoms is if its running like complete $h!t

1 Rotor =
wont' hold idle, backfires a ton after u let off gas, has a very hard time revving up past 3-4000rpm, the higher you rev it the more it backfires, also if you take off apart the intake manifolds etc , youll notice one side will be all black inside from it running on one rotor

2 rotor running like 1 rotor =
could be one or a combination of -
vacuum leaks sucking in unmetered air (causing backfire), bad spark plugs/wrong plugs (or connected improperly), exhaust leaks, low compression, bad throttle position sensor etc

sparkscarz

im gonna try this. but would it be accurate? cuz between 80 and 90 is a pretty fine line. id assume the test would have to be as accurate as possible right?

RotaryEvolution

iTrader: (30)

there's tons of variables but if you have anything above 80psi then the engine should be running somewhat fine and have almost no issues starting.

cranking RPMs relate to compression and mazda has a chart for compression figures versus cranking RPMs. the general rule of thumb is 250RPMs and 85+ psi even on all 6 faces means the engine is fine.

i never cared for the poor man's test either. an easier method for that is remove the EGI fuse, hold the throttle wide open and crank the engine while listening to it. if it is cranking perfectly even without any skips then you likely have no problem with the engine. it's actually harder to hear dips in compression with the plugs out listening for "wooshes" than it is listening to the starter struggle.

sparkscarz

well it does backfire but only when i delcel or if im reving high. but i can go past 4 grand rpm easy. also i took my throttle body off and i did notice the single lower throttle plate and intake runner being ALOT cleaner then the dual upper plates and runner that had a lot of deposits . could this be a sign????

i have no vacuum leaks (not 100% sure) i just put in new plugs and wires. pretty sure there connected properly. im currently running a RB true dual with only mufflers. not sure bout compression. but yah i do need to adjust my throttle position since i took off the TB.........

sparkscarz

awesome im gonna try that first. but yah my car has no problem starting at all. ive had it for bout 6 months and it has started every single time....

what got me worried is that my dual upper throttlw plates and really gummed with carbon but the lower single throttle plate is clean enough to eat off of.... is this tell me something?

wthdidusay82

iTrader: (15)

is the car a non turbo ? if it is, does it have functioning 5/6 ports ? if they're removed it can cause problems idling and possibly more backfire, my old s4 na (streetported and full headerback exhaust) had it's 5/6 ports/rods removed and i also had a ported throttle body, caused it have alot less power in mid/low rpms, but supposedly gives a few hp on the top end.

if it was blown and running one rotor it would be completely black on one side of all your intake and exhaust because nothings burning out. i know this because mine running on one rotor looked like that

RotaryEvolution

iTrader: (30)

the dual throttle plate runners will always be gummed up, turbo or non turbo doesn't matter. those ports are only used above 4k RPMs and until then the intake resonance pushes engine oil back up into those ports.

if it runs fine under a load up to and beyond 4k RPMs then i doubt you're running on one rotor. with only one rotor it would feel like a diesel rabbit taking about 3 minutes to get up to 45 mph.

sparkscarz

it is a non turbo and yes it does have the 5/6 ports and no curently they arent working but i have them closed for now. would it simulate a 1 rotor operation ?
i also have done the throttle body mod and i ported it. did i just waste my time? looool

but yah the lower intake runner after my throttle body is clean and uppers are dirty enough to be exhaust ports ... should i be worried?

sparkscarz

ohh i didnt know that oil gets pushed back up to the tb :s since i got no insurance i cant really drive my car around so i wouldn't really know if i runs good under load. im gonna do a compression test and ill know for sure but thanks ill get back with the results

wthdidusay82

iTrader: (15)

the ports i think are suppose to open around 4000rpm so if your car doesnt seem to be running right after that , thats probably why. they work like vtec does in a honda in a way, so having them shut will be a restriction in the intake system