9 replies to this topic

[stevemkeen]

Hi all, 

Hoping to get some advice concerning the reason why my Gaskets and decompression plate would blow through so quickly after a 2 weeks of use, see pictures

I have supercharged a 998 CC engine from a 1985 mini city, the engine was striped and taken to the machine shop who rebored it and fitted the standard flat top +20  thou pistons, the block deck received a 5 thou skim to clean it up.

 

Fitted a swiftune SW5 cam , centre oil pick up and new oil pump after I ported the oil entry/exit ports to the oil pump to help oil flow. all other component within the engine where checked and new crank bearings fitted.

 

The supercharger kit was bought about 4 years ago from Jonspeed and comprised the eaton supercharger along with a CAM4810 head which had some porting already done.

Kit came with decompression plate and gaskets and replacement fuel needle.

 

Ignition is via an coil pack driven from a Nodiz pro mappable ignition drive system fed from a trigger wheel and works reliable so far and was easy to instal and set up.

I know that compression ratio is important and as you can guess perhaps I didn't put enough homework into checking it would be correct for my application.

 

I have used the Podifold Mini engine compression ration checker available here   http://www.podifold....ompression.html

and entered the following spec

 

Piston size 998/1098 cc +20 thou

Crankshaft 998

Head gasket 2.8cc

Decompression plate 5.8cc

Piston CC =0 cc - flat top pistons

Cylinder head volume 21.4 confirmed by measuring

Piston deck height 22 thou , confirmed by measuring

 

This calculates a compression ratio of 8.88

 

Question i would appreciate some advice on is the following

 

Is this compression ratio figure correct and would it be something that my engine and head set up could reliable work with the supercharger fitted.

Another question, is my base ignition timing (shown below) I have loaded and run suitable with the increased pressure that exists during combustion with the supercharger.

Engine ran very well, temperature was normal, using a HIF44 carb with the supplied jet needle supplied with the kit, used colour tune and didn't show it running lean at all.

 

RPM / advance

800 / 10

1200 / 12

1600 / 14

2000 / 15

2500 / 18

3000 / 20

3500 / 23

4000 / 25

4500 / 29

5000 / 29

5500 / 31

6000 / 32

6500 / 33

7000 / 34

7500 / 36

8000 / 39

 

Any advice would be greatly appricated.

Attached Files

•  Blown gasket 1.jpg   59.3K   23 downloads
•  Blown gasket 2.jpg   80.65K   14 downloads
•  Blown gasket 3.jpg   64.72K   28 downloads

Edited by stevemkeen, 26 June 2017 - 07:17 PM.

[Turbo Phil]

Far to much ignition advance for a boosted motor. I'd be thinking something like 24degrees as a maximum, possibly less. The compression ratio is also on the high side. I presume you're using the Eaton M45 ?

Phil.

[stevemkeen]

Phil,

 

Thanks for reply, yes it is a eaton M45, I'm very new to this as you can probably tell, just beginning to realise how important Compression ratio is , would the timing profile i used be more likely to cause the blow through of gaskets I've seen, would other effects likely to be observed with the engine running from this ignition map, nothing stood out when it was running, it failed all of a sudden began to hesitate, it back fired then stopped and wouldn't start, oh yes and steam coming from around the gasket area.

 

Will alter my ignition map before running it again, Are there any ignition profiles posted anywhere for similar setups i have put together.

[mini13]

wow, yes that looks to be way advanced,

 

 

have a look at the below, not that it is rpm agains load ( boost) in kpa, 100 php is approx atmospheric, so below that is vacum and above boost, 200 kpa is approx 1 bar boost (14.7 psi) you can roughly scale the map from that, maybe pull a couple of degrees out at boost just to be safe.

 

 

http://photobucket.c...3MTgwNzk=/?ref=

 

I will say that running a pmap like you have it is easily possible to destroy the pistons, I would highly recomend doing a leak down test without and with oil to check for possible ring land problems.

[Gr4h4m]

The introduction of a simple water injection system will also help with intake temp, switched at 5psi will help and fired into the mouth of the charger.

[HUBBA.HUBBA]

Far to much ignition advance for a boosted motor. I'd be thinking something like 24degrees as a maximum, possibly less. The compression ratio is also on the high side. I presume you're using the Eaton M45 ?
Phil.

+1 on the max 24 degrees and High CR comment
Also make sure all the surfaces are properly flat

Edited by HUBBA.HUBBA, 27 June 2017 - 04:26 PM.

[timmy850]

Do you know how much boost you were getting?

[hazpalmer14]

Do you know how much boost you were getting?

 

all of it

[stevemkeen]

Hi all,

 

Thanks for all your comments, I intend to do much more home work and learn a thing or two before completing the rebuild and posting comments, today had a talk with stuart from Vmaxscart  who was very helpful and confirmed all the same comments you guys mentioned, bought a thicker de-compression plate with good quality Payen Gaskets which i'm confident will lower the compression ratio to a more acceptable level ,will do the measurements to make sure.

I also intend to install and unitise a 3 bar load sensor to use with the Nodiz pro mappable ignition system and have a season on the rolling road , thanks for the help.

[mini13]

Yep stu's a good bloke.