Has anyone on here with a full or half bridge ever have a compression test with a known good engine.
Im trying to work out what sort of numbers you will loose over a stock port etc
Thanks in advance
I was told that it was pointless compression testing a \'bridged\' engine... why are you asking ?
well we are trying to work out why my engine has low compression, whether the ports are causing the low comp or if its a clearancing issue, i dont think its been built incorrectly as all the faces on both rotors are low, its not gonna be that a mistake was made on every seal etc
The car starts from hot and cold and makes good power, hence wondered if the porting makes a big difference to numbers like i know PP does
I thought you only had a Pineapple templated \'street\' port? :confused:
What clearances were used on the side seals?
What Apex seals were used?
What corner seals?
Were the apex seals clearanced?
Were the housings verified good?
Define low on compression.
When I tested Eds engine (massive street port) it gave readings all in the 8s iirc. Porting does affect compression values but not that drastically IME. I beleive martin at Speedline sold a half bridge once that also showed 8s on reworx tester.
Also following on from sihs post, side seal clearances are critical to compression. Different apex seals also have varying sealing charfteristics. For example mazda seals seal well under all scenarios whereas a one piece hurley race seal doesn\'t seal well from cold but they expand and seal much better when warm (according to Mick hurley).
What rpm\'s are you testing the compression at ? Week starter motor\'s or tired batteries can give a low cranking speed and consequently low compression results. The field service manual has a correction graph that shows how much to factor it up by.
intresting.....!....didnt steve warranty the engine?
Quote from: SiH;695609I thought you only had a Pineapple templated \'street\' port? :confused:
What clearances were used on the side seals?
What Apex seals were used?
What corner seals?
Were the apex seals clearanced?
Were the housings verified good?
They are racing beat template with a big enlargement on the opening(so the corner seal is supposted 50%)
0.05mm was used on the side seals
all atkins rotary master kit
yep
yep, used different ones
Quote from: Jit;695636Define low on compression.
When I tested Eds engine (massive street port) it gave readings all in the 8s iirc. Porting does affect compression values but not that drastically IME. I beleive martin at Speedline sold a half bridge once that also showed 8s on reworx tester.
6.1-6.3 on front housing
5.7-6.0 on rear housing
Quote from: Prof;695638What rpm\'s are you testing the compression at ? Week starter motor\'s or tired batteries can give a low cranking speed and consequently low compression results. The field service manual has a correction graph that shows how much to factor it up by.
Done at 240rpm on both
Quote from: Ed_RX7;695641intresting.....!....didnt steve warranty the engine?
Yeh the engine is warranteed, he isnt sure why it should be so low.
You could imagine if he made a mistake on a side seal, one face would be out, but for all faces on front and rear rotor tells us it must be something else.
Hes built loads of engines now, Rotorbunnys car had 8-7.9 on all faces so its not like he cant build an engine and he was extra careful on mine because he knew the power i wanted from it.
The only thing we can think is maybe the ports, hes used the same sized ports on his racecar which is almost finished, so hes gonna run that in and see what comp results that gets.
If they are down then we know its the porting, if not then theres something else wrong.
The car starts from hot and cold everytime and makes good power.
He also said run it for another 3000miles, if the comp drops then we know its an engine problem and will get it sorted no problems, but we both want to see if we can work out what is causing it before a strip down
Just wasnt sure how much porting effects results, that was all
Don\'t worry about compression as long as it\'s even and it starts fine hot and cold engine your driving. Different porting does give different compression results, as do different compression testers. Side seal clearance is bigger than what I would do personally but that\'s a personal thing not a generic rotary rule. What\'s ggod for the goose isn\'t necessarily good for the Gander so no point try to compare what someone else has got unless everything is a direct like for like only then can a meaninful comparison be made.
rgds
Brian
fair enough. what vac readings are you getting on idle?
Quote from: turbotoaster;695672They are racing beat template with a big enlargement on the opening(so the corner seal is supposted 50%)
0.05mm was used on the side seals
all atkins rotary master kit
yep
yep, used different ones
6.1-6.3 on front housing
5.7-6.0 on rear housing
Done at 240rpm on both
Yeh the engine is warranteed, he isnt sure why it should be so low.
You could imagine if he made a mistake on a side seal, one face would be out, but for all faces on front and rear rotor tells us it must be something else.
Hes built loads of engines now, Rotorbunnys car had 8-7.9 on all faces so its not like he cant build an engine and he was extra careful on mine because he knew the power i wanted from it.
The only thing we can think is maybe the ports, hes used the same sized ports on his racecar which is almost finished, so hes gonna run that in and see what comp results that gets.
If they are down then we know its the porting, if not then theres something else wrong.
The car starts from hot and cold everytime and makes good power.
He also said run it for another 3000miles, if the comp drops then we know its an engine problem and will get it sorted no problems, but we both want to see if we can work out what is causing it before a strip down
Just wasnt sure how much porting effects results, that was all
at around 900rpm im getting 16-17in on the gauge and 320 on the pfc
hmmm ...thats seems a bit low ....but not sure on what other half bridgers have......your probably gonna have to pull it and see whats up internally
If the engine is running fine then leave it alone until it really is obvious that it needs something doing.
Compression on bridges should be capable of being higher than that,but as long as it runs it is dynamic (Engine running) compression that matters and not static (Engine not running) compression.
Regards
Carl
Hey carl, i assume theres no way of knowing what the dynamic compression is?
If an engine makes good power(will find out tuesday) for the boost it is running should we assume that the dynamic is good.
ie if its bad would the power be down(like boost is escaping past the rotors)
maybe uve heated it up a lot and warped the apex seals
its only ever ran 10psi of boost up to yet, never been above 100c water or 47c air temp.
Surely if the all the seals are warped id be down on power, ill see what carl says to my last question
its running fairly rich aswell so cant imagine it would be that.
Will find out shortly anyway when steve finishes his race engine, plus he will fully cover me until i stick a massive turbo on anyway so if it does turn out theres a problem he will strip it down for me.
If the engine starts hot or cold and also under boost and load it runs fine then dynamic compression will be fine too,If seals are warped then it will be hard to start especially hot,also you can end up with pre-ignition in that state due to combustion gasses getting into the chamber following and causing it.
Regards
Carl
thanks for you help carl.
You dont happen to have any second hand airpump delete pulleys do you, dont mind if greddy or ebay version
Quote from: turbotoaster;695861thanks for you help carl.
You dont happen to have any second hand airpump delete pulleys do you, dont mind if greddy or ebay version
Sorry,I don\'t have any.
Regards
Carl