rotayt

hey people my 13b bridge port with ida was getting dyno tuned yesterday got all set up on the dyno, set the timing with the iming light and locked the dizzy,



done a first run and found the ida needed to be modifyd took it apart and was jetted out to suit and took out a wall in side the ida for more fuel.



assembled the ida an put it back on and started the next run checking the air fuel ratio an all.



it got opend out to 8000 rpm and it sounded like it rev limited and he picked up sumthng on the knock sensor



as it came down to idol it sounded like like a 6 cylinder



turned it off and he checked a few things out at first he thort he broke a tip on the spark plugs



culdnt find anythng and then we did a compresion test ,the thing he picked up on the knock sensor was a breaking apex seal



and the front rotor was down on compresion aswell , but it had definatly broken a rear apex seal



the motor is roughly 600km old from a brand new re build new housings carbon, apex seals,new bearings with extra windows







im so gutterd about this as i have been building this rx7 up for 3 years.







i am going to talk to my engine builder and try find out why it has done it and hopefully come to an agreement.



as the engine is warranted for the engine build



iv always warmed it up befor i drove it never thrashed the crap out of it always run premix





any help on why you think it has done this will be greatly apreciated, is it the dyno tuners fault?? or the build i dont know

vosko

nothing got sucked in it ?

rotayt

i dont thnk it did

Lynn E. Hanover

Missing spark plug tip and a broken apex seal?



Spark plugs break up due to: overheating from too high a heat range, and, or, detonation, If its an NA engine detonation is difficult at high RPM. and, or, too much ignition advance. Or premixing a top oil that does not burn ash free.



Were these carbon apex seals?



The other option would be cross talking between the front housing and rear housing ignitions.



Typical of the old stock igniters.



Or, if the engine has a electronic controller that had a sensor telling it a story about one of its parameters. Like picking 44 degrees of advance because the engine detected very high manifold vacuum where none exsisted. (controller thought it saw high RPM closed throttle for an instant)



If you know you will be using maximum power high RPM for more than a few seconds, put in ice cold racing plugs, leading and trailing. You might foul a plug now and then but it won't cost you an engine.



What jets? what emulsion tubes? What choke size? Did you remove the filter in the bowl cover?



Did you drill out the port above that filter? Did you raise the float until the boosters just startd to drip, and then just lower it a hair? Did you jack the fuel pressure up to 6 PSI and can your pumps hold that pressure at 8,000 RPM. Can you hold EGTs below 1600 or F/A below 12.7?



You should be able to produce maximum power at 25 degrees of advance checked at 6,000 RPM with 97 octane or better fuel. With crap fuel you can run 20 to 24 degrees maximum and maintain great reliability.



Or it ate something solid.



Lynn E. Hanover

rotayt

thanks for the reply, it is a na engine no computer and yes carbon apex seals , new coils everythng







im goin over now to find some info out and talk to some people



i will have the info you want tonyt



thanks jo

rotayt

wat a day!!!!!



went to tauranga to see what was gunna happen got told i could take motor out an take it to engine builder sooo i went bk to waihi picked ute an trailor up thanks heaps to ma mates for borrowin it to me, went to dyno power pickd rx7 up took it bk to dads shed got down to it an took the motor out..................



was just in time to drop it off in tauranga hahaha so it will be getting taken apart an assed by the builder.



i had a look at the apex seals through the exhaust, clearly broken on the ends on a couple in the front an bak



sooooo i need to find out why that would happen i heard of poor clearance??



and i heard from some one if you use the round middle corner seals they can break the carbon apex ends???



i dunna but it was not dry in there,, the middle of the apex seals lookd good aswell



any help would be great

Lynn E. Hanover

Carbon apex seals require .0045" to .0055" end clearance. Look for burned ends on the apex seals,



And brown to black tracks on the irons where the seals have been pressing hard. Otherwise it was not an end clearance problem. You can check clearance yourself withdial calipers. Find the narrowest measurement of the housing, and subtract the longest apex seal. Should be .0045".



Lynn E. Hanover

j9fd3s

when i was getting stuff together for the PP motor, and i mentioned the carbon seals, everyone was really quick to caution me about detonation.



i thought this was weird, as it's NA, but ive decided its better to be safe than sorry. i'm gonna make damn sure the fuel is not too lean before i start advancing the timing (being a PP ive just set it up like in the competition book)



also the carbon seals were a little big out of the package, unlike the steel seals.

rotayt

lynn hanover..........

thanks for the specs i will definatly look in to that , the engine builder has theengine atm an hes shut till 11th january



very disapointing.........

owell thngs happen and ya gotta deal with them!





J9FD3S................. oh really weird if you find out any more info on the carbons let me know!







im considering just going pp hahahaha







thanks guys for the help!!!!!





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