I was kind of expecting to have to rebuild the engine some time, but it never is expected.

I thought it would go out with a bang since I never bothered with the tuning. since it still has some compression in the rear rotor I don't think it is the SC fault.

I'm going to get it checked out by the local shop to see what they think.

 

Didn't you get a crack at the dowel pin earlier ? Whatever caused that would have weakened your seals and they were ready to go at any time ....

 

not that I know of. there was a slight oil leak on the front housing but not enough to hit the ground or loose enough oil to worry about.

 

I couldn't stay off boost for too long.

I tested it out a little today to around 6000rpm and it is still fairly smooth under boost.

the new pulley combo has boost starting around 3500rpm and should hit 300g/s at 8000rpm.

 

When I blew my apex the motor was still very powerfull under boost - could not even tell there was anything wrong . Just couldn't get the bitch started without a push ....

 

thanks brettus I was thinking that the SC might be masking a problem.

I haven't lost compression totally so it may be a stuck seal or side seal issue. I'm just guessing

 

the plot thickens...

the SC has been masking a problem. local mechanics say the motor is low on compression but not worth doing anything about.

since going back to NA and having a chance to log some airflows it is obvious from the lumpy and low MAF readings the engine isn't breathing what it should. the MAF kind of flattens off after 6000rpm and there is little gain. highest flows are 189g/s @ 8000rpm for cold weather runs (15deg)

I think the aux-ports are partial blocked with carbon.

 

189 g/sec? N/A cars move more air than that!

 

yeah - the SC was masking your low compression by the sounds of it .

 

that was N/A I would expect 200 odd. that was the highest. most are 170-180 odd.

last October the SC hit a maximum of 295g/s on an unscaled maf @ 8psi and since then it has been going backwards which I attributed to other possible causes.

 

cleaned the aux-ports out directly today. it seemed to help. the car was hitting 207g/s consistently and sinning the wheels on gear changes it hasn't done that NA for ages.

 

Despite all the hassles and hurdles Jarl, I'd say that you're still having heaps of fun!

Cheers,
Danny

 

it is certainly not fun all the time, but it is a hobby. I enjoy making the parts on the mill the best; the constant fault finding is getting tiring. what makes it worse is that the problems are not the SC just a weak motor.

 

the supercharger has been off the car for a number of months now. the car seems to be running ok but now and then it still has hard start issues.

more boost has been a goal for about 6 month now. working around the standard water pump and alternator drive set and the additional supercharger drive pulleys has been a challenge due to a very limited selection of belts I could use.

I finally found a belt and pulley combination that would suit the SC drive ratio and belt length. I went ahead and had a new set of pulleys made that jumper the std 5 rib belt up to a 6 rib for more positive drive one the supercharger.



I bolted the pulleys on and went to order a new belt. the last belt I bought I cut to test the fit. after a few weeks wait the shop got back to me and the belt is no-longer in production

the belt was from some dam fiat built in the 90's only sold in Europe. I must have been the only one in Australia buying the belts.

I can still find a few of the belts floating round but I have to order from Europe and wait. funny thing is I'm buying a Australian made belt from Europe and saving $20 after paying for postage back to australia.

 

I have come to a major change in design philosophy on this project.

I had always intended to place the throttle body in front of the compressor. with this arrangement you don't need a bypass valve, and pumping efficiencies are increased at part throttles and vacuum.

having the throttle in front of the compressor was creating throttle response issues due to the front mount intercooler and the long length of pipe work.

while I have tuned most of this out with careful sizing of pipe work and intercooler there are still some issues.

with the current 10psi I'm wary of full throttle but the in gear performance still seems dull. in 4th when you put your foot down from 60km the car just doesn't seem to pull the way if should. there is plenty of boost down low (not full boost, but 5psi isnt to shabby for a centrifugal SC @ 3000-4000rpm).

I have decided to try a more conventional setup and move the throttle back to its standard position. to do this I need a bypass valve to give the boost a partial throttle somewhere to go.

I ordered a synchronic BOV from BHR (forum vendor). BHR has always given me great service and I have purchased spark-plugs from them previously the have come in handy. BHR is my first call for parts.

why choose the synchronic BOV as a bypass valve?

I don't pander to the hype and marketing surrounding this BOV. having opened a few BOV's in my time ranging from diaphragm designs and piston type valves. they all operate on the same principle. the synapse engineering design is a very good one and possibly better then the others I have pulled apart.

the big seller for me is the normally open nature of the valve, tune-ability of the valve and it comes with plum back fittings as standard (necessary for the MAF and flash tune). it is also reasonably priced compared to other BOV's.

that it solves the last little issues I have.

 

Sounds like a good plan .
I like the way the Synchronic works as well . However , after studying it I just decided to tune my turbo XS to work in a similar fashion - ie open at idle and cruise . It really works well like this but must be recirculated .

 

You will like it - I have gone through a half dozen BOV's before settling on that one - and now I own two; and all my friends have them as well.

 

does having two double your whp ?

 

is the sc back on or off now?

 

Yes, when you have two cars that need 'em!!!!!!!!!

 

the SC is back on and running over 10psi. I'm going easy on it till I change the throttle position and fit the BOV.

the motor seemed ok when the SC was off and would start. now the SC is back on it sometimes starts sometimes it cranks for ages but will usually start. the higher boost must have changed the starting characteristics if I'm right the BOV should cure it.

I'm also still on the old slow starter motor and not the faster starter that some .au owners got under a hard start recall. if I had the faster starter I'm sure it would start much better.

 

there sure are some crap BOV's on the market but a good bypass valve for a SC is one you don't know is there.

since boost is being created all the time, at part throttle they vent constantly. when vented to atmosphere they are a never ending BOV sound. I really don't want that type of noise.

 

6 rib belt and the boost is still pulsing.

I doubt the belt is slipping as the behaviour didn't change with the extra belt width.

 

after a few days with the synapse engineering valve it seems like it has its good and bad points like any product.

the valve is easy to open and the different vacuum sources do seem to have a big effect of the valve tuning.

it seems well made but for a valve that come and recommends plum-back installation the recirculation fitting is a joke.

it is held in by one grub screw that dosen't even retain the plum-back fitting. no wonder they recommend gluing it in with silicone for MAF based cars. a second grub screw would prevent it. sloppy design IMO.

they could also include some t-pieces for hooking the thing up. it even recommends and describes the use of two T's in the instructions. luckily defi are generous and I have one lying round.

 

Pulsing boost very well could be "overlap" across the 2 rotors from a bad seal...