compretion ratios/boost/heads help help help
Turbo Mini Forums

hi people, sorry to burden you all with my problems. i have a relativly high spec 1293 turbo, that i jus cant get to run right, i appreciate low comp turbo will be somewhat boggy, but the car jus wont build rpm out of the turbo even on the slightest gradient, tho if i use the chocke the bogging dissapears all the way to the red line with devastating mpg. i initially thought must be fuelling, tho tried every needle, gas annalysers etc with only minor improvements, i have 16cc forged pistons, an a avonbar de beaked hi boost head tho im only running 10 psi, the so called EXPERTS who built the engine have now told me its never gonna run right at 10 psi due to such low comp ratio, so we tried a standard N/A head to bring the comp up an it runs better but its far from perfect,, can i successfuly run 10psi with the original set up or do i have to bin my £500 head, would fitting the T2 turbo help this set up? Any help would be hugely appreciated as i feel i am banging my head against the wall. chears

mate lets get one thing staright from the off old chap.

dont dispere we all been there done that and got the t shirt on new engine woes.

so my sugestion is its all down to feuling and ignition settings.

carry out all feul pressure checks ( do a serch on these).

then its time to check ign timing , depending on your dizzy type i would set at about 12 deg at tick over if you have mechanical advance.

then wind out your mixture screw so you get about 7-8 co at tick over then take her to a decent rolling road for a good custom needle and ign set up done.

one thing to look out for in the mean time is not to boot it with boost as you can soon melt pistons.

but look at your boost gauge when you are cruising say at 2500 to 3000 rpm and it should hold a vacuum at about -12 psi if it soon climbs to 0 when you are at partial throttle openings then you are to lean at this point so richen the screw again.

all the above is just to get you to a rolling road and nothing else.

good luck and keep us posted

always looking for them bigger bunches of bannanas

What CR are you running with the good head on?

Not sure what the EXPERTS are on about as whatever maximum boost you run will have little/no impact on the power off-boost or when the turbo is spooling up.

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

chears for the advice its much apreciated, so running 10psi with 16cc pistons and a high boost head is not imposible as it seems. i contemplated skimming the head to raise the compression ratio but theres only so much you can skim an is it really nessaccery, but in your opineon you suggest its more set up than the issue of compression ratios?

i know its sound daft but im not 100% sure iv been told with that set up ie, the good head im running somwhere in the sevens, as apose standard met turbo which is in the 9s

have you been set up on a decent mini turbo friendly rolling road?

it sounds like the car needs it, otherwise you will be throwing money away and not reaching any improvements before it goes bang

yeah i apreciate that delicate fact, but i feel i should try to be sure of which route to go down, in terms of a head and commpression ratios, i wanna establish a set which is going to work well before i waste even more money, fine tuning a set up which could be wrong from the off.

North London - Peter Baldwin is not that far....

I'd say you also need to definately establish what your CR is. Just knowing it is "seven-ish" isn't really enough.

I'd say don't dispear just yet, a decent setup will probably cure a lot of your problems. That the engine picks up and accelerates OK when the choke is pulled out speaks VOLUMES and points to it being way too lean.

What cam are you running?

£/bannana a good rolling road is the way to go

it was running a very rich needle, iv gone backwards to an early met turbo needle, useing the chocke clearly results in overfueling, but could this some how compensate for a low com ratio in terms of performance, does the fact that i can make the car pull like a train from 2500 rpm using the choke suggest the prob is not the compression ratio?

im running a minispares turbo cam, nothing wild, its suppost to very progressive

its not the compression i can assure you!

even in the 7s on boost it should rip your pants off!

imo fit the turbo head back on which came with the engine
then get a 12psi boost needle from Mr AVONBAR!

then check all the above what the guys have said

next have you tried the "T" Piece trick????

if not do a search on this forum and get that done!
this could well be your problem.

next get to peter baldwins rollers
who is the top puffler with the rollers.



Peter Baldwin - Rolling Road
Wilsher Garages Ltd.
18 Cambridge Road
Wimpole
CAMBS
SG8 5QE
tel. (01223) 207217

Peter has had over 40 years experience in setting up performance cars. He races Mini miglias in his spare time and is quite well known in the Cambridge area.
peters enthusiasm and professionalism is second to none He really knows his stuff !

EXCELLENCE COMES AS STANDARD:

a nice guy who you realy feel at ease with.

if you have a choice this is the man:

and he will make you a brew as well



"i cant speak more highley of this man."

Edited by BENROSS on 21st Jan, 2006.

Most certainly fuelling or ignition, or most likely a combination of the two.
Low compression will not help the motor pull from low down, big cams and tall gearing will exaggerate this. But it should pull if revved hard enough.
My motor is 7.8-1 compression and quite "cammy" but i can use mine on the road no probs, and it will pull cleanly on hill starts etc.
Firstly check the timing, i found i needed a lot of advance low down to get it to pull away properly. I tried 15deg at 1,500rpm and it was awful, swinging it to 18deg made a huge improvement. Though if doing this YOU MUST BE CAREFUL not to run to much total advance, otherwise you'll run into deonation problems.
You need to know what your fuelling's doing as well though, it's no good just guessing. It's all to easy for it to go tits up !
My advise is basically the same as others, get it to the rolling road, where you can monitor what's going on properly.

Phil.

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