newly rebuilt engine - poor compression figures

[Rzla]

Carl, i looked at a car that had been bridgeported and built by you, blue fd in Oxorfd, cat c damaged, the chaps name escapes me atm
compression test after 1600 miles was low 7\'s to mid 6\'s on 1 rotor and low 6\'s to high 5\'s on the other,

i remember the diff being a maximum of 1.3 bar, from front to back rotor.
 we called you up there and then and you said it was what you expected and not too worry, you\'d still be willing to warrant the motor but wouldnt tear it down because of those figures.

so i dont understand how you can say having 6bar in really poor here when you told me high 5\'s where fine,

Its called double standards and being a hypocrite :Nono!

What he said to you must have conveniently slipped his mind... selective memory

[Prof]

I belive his post says 1600 miles which is more or less the same?

Didn\'t spot that - doh :p

[Mir]

I know a car built by jaydee, the compression on that car is still above 8s and the idle on that car makes me feel like selling my 20b.. The car by the Grace of God works perfect and the compression is look, having said that the engine was built over two years ago.. So saying that having 5 and 6 does not look normal.. I just talking from experience.. Carl is expert and knows wats right..

Syed

[Mir]

Sorry meant compression looks good and perfect.. I rate jaydee for builting that car...one of my favourite Fd that has been built to precision...

[HaywardRotary]

As for fuel in this country Pete we have found that Shell V power is pretty consistent,but I have heard the bad reports from Australia so maybe it\'s a country thing.
Regards
Carl

[HaywardRotary]

Hi Gary,
The car in question had an issue with compression that was reported to me by you, since I said that I would waranty it then why should you have to worry? I would have liked to do the compression test myself but that did not happen. if after that the test was still the same I certainly would have done something about it,but until I personally saw the results it wouldn\'t have been torn down, and we allway\'s compression test in front of the customer so they can see what we are doing.
I have done compression test\'s and noted vastly differing results from other people\'s results and found that it is allway\'s best to do it yourself and then you know the animal at that time.
I remember being at rotorstock a few years back and watching someone doing comp test\'s and charging people for it,I remarked to the person concerned that he should give the money back to those who had it done at the time because it was being done wrong!!! They weren\'t opening the throttle on any cars they were doing it on! so effectively giving false readings and some people were being told they needed rebuilds when they didn\'t.

Recently we compression tested a car over a few months that was built by someone else,it has 12,000 miles on it and was not used for some time, before tuning it was in the 6 bar range,since tuning though the compression has consistently gone up from 6 bar to 7 bar and now just under 8 bar,all down to decent tune and regular use. Suprising eh? But it is a fact.

[HaywardRotary]

The main thing that really varies compression on a rotary is not porting but the type of seals used. one piece give much lower static compression than two piece.
That having been said one piece with lower compression do not necessarily mean a bad engine.

[suba]

just reading through this ...if the tuner noticed high knock why would they comp test the car unless they knew it had det......

hmmmmm sounds like they reliased and then thought oh fduk.....better check.

Just stating what i think it looks like...if i\'m wrong then apologies to all.

I was there when it was being mapped, and they were at a loss at to why there was knock, even with timing pulled out as much as possible - hence the compression test.

[PGiljevic]

I was there when it was being mapped, and they were at a loss at to why there was knock, even with timing pulled out as much as possible - hence the compression test.

In tuning hundreds of rotaries I have come across the odd occasion where something similar has happened. One of those was later identified to be where the owner (self mechanic!) had rewired his coils incorrectly (low tension side) and basically it was firing the Trailing pug before the Leading plug! Checking leads obviously had no influence as it was in the harness!

This could be one reason for unexplained knock (among many!) but just an idea of what to look at.

No amount of timing reduction or drowning the engine in excess fuel would stop the knock from happening at ~6000rpm.

In one other case I had another customer who had the exact same thing,a nd it was traced down to a car alarm! of all things! which was spliced into the ECU, changing the loom cured it. :2Confused

These are but two "odd ball things" that have happened over many years, but are things that could and did happen.

[steve garbutt]

Hi Gary,
I remember being at rotorstock a few years back and watching someone doing comp test\'s and charging people for it,I remarked to the person concerned that he should give the money back to those who had it done at the time because it was being done wrong!!! They weren\'t opening the throttle on any cars they were doing it on! so effectively giving false readings and some people were being told they needed rebuilds when they didn\'t.

Recently we compression tested a car over a few months that was built by someone else,it has 12,000 miles on it and was not used for some time, before tuning it was in the 6 bar range,since tuning though the compression has consistently gone up from 6 bar to 7 bar and now just under 8 bar,all down to decent tune and regular use. Suprising eh? But it is a fact.

Haha sorry for my bluntless but that would be Rixio, beer Saturday night and all that haha
hes a smashing guy :Ladys-man

[steve garbutt]

but crap at compression tests haha

[suba]

The main thing that really varies compression on a rotary is not porting but the type of seals used. one piece give much lower static compression than two piece.
That having been said one piece with lower compression do not necessarily mean a bad engine.

What would you expect an engine running PTS 2mm apex seals to show as far as compression is concerned?:xconfused

[PGiljevic]

What would you expect an engine running PTS 2mm apex seals to show as far as compression is concerned?:xconfused

Not very much :flamed

I have a few on file (3500km old) showed on average -10psi or more less than a stock Mazda seal, and after 5000km the apex seal wore down so much it fell out of it rotor groove .......

Not a nice thing for you to read, but like I said before I will say if you ring Glovers and complain they WILL tell you "they were NEVER made nor intended to be used in road car applications" and they will give you EVERY EXCUSE under the sun why they wear out so fast and so on. Lots of people get get sick of replacing them at every oil change interval :rollin

Stick with mazda apex seals :Thumbsup! there is nothing wrong with them and they last 100 times or more longer.

[suba]

A bit of an update on this:

on stripdown and inspection - Rear housing scored (now replaced), some marks by the plug holes on rear housing (heat related?), and and hairline crack in a cornerseal (again rear housing).

Any more ideas chaps?  Ignition / fuel related?

Next port of call is to get the engine comp tested before it\'s back in the car I guess?:Thumbs-up

[HaywardRotary]

Corner seal cracked would denote a detonation episode.
Regards
Carl