help on loss of power
Turbo Mini Forums

Just to add to the low comp etc I'm running 1.5 rockers !!!!!

Turn the boost up. This is the only logical solution.

Who used to say that the ph2 is a 'hungry cam'? Benross?

In the 13's at last!.. Just

GT20what?

WWW.TURBO-MINI.COM

Or wind the boost up to 30Psi

I will say I'd be supprised that you would drop so much hp from th cr reduction, so do check the cam timing first, Tom knows what hes doing obviously, but none of use are immune to a cock up!

Other than that, it's either skim the head to fuck, or wind the boost up to 30 psi....

the GT2056 is nearly on the surge line at 2:1 pressure ratio and 10 - 11 Lb/Min air.

What you might find is that the exhaust back pressure is greater than 14psi. With such a large overlap, compounded by the 1.5:1 rockers, results in exhaust gasses exiting the intake, and not the exhaust. One reason why high boost on racey cams works well...........

Measure the exhaust back pressure before the turbine, during a power run and compare that with the inlet manifold pressure. You'll maybe lucky to get it below a 2:1 engine pressure ration. That is 30 Psi exhaust, 15 psi inlet

Edited by Sprocket on 7th Jun, 2017.

Wow bigger can of worms for me to look into .
Phil yes its a 2056 , exhaust is 2.5 all the way through with very little restriction in the back box .
Im not planning on going back to the rollers until ive worked it out !

Colin how would the exhaust back pressure be measured ??

Edited by cossierick on 8th Jun, 2017.

what dose the engine read on a normal compression test? 90psi? 7.5 is really low imo that thing wants plenty of boost

I concur with Sprox, take the 1.5s off.

They work really well on Kent cams (which by all accounts were developed with 1,5s).

But they've always been shit on pipers. Also didn't work when I tried a PH2.

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

I've done a lot of simulation work on what may be the ultimate 5 port using a 1293, GT2056, 1.5 rockers and the "Nic" cam which is not dissimilar to the Ph2. It's true that the GT2056 is the bottleneck and a change to a GT22 added 30hp without any other changes because it opened up the exhaust side.

However, in this case, I don't think it is the turbine side of the turbo causing the problem simply because there is not enough air flow to cause significant back pressure.

I think that the cylinder conditions at spark are poor. Too much fuel and not enough pressure for decent ignition. Just a theory but I would either lean it off a bit or wind the boost up.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I like all the suggestions to wind the boost up

If something is worth doing, it's worth doing half of.

Thank you all so much with you help i really do apreciate it .
Compression test is happening tonight and i will post my findings !
Tom might be able to confirm this but i think the cam is timed in at 107-1/2 , that is going to be next week until it can be checked im afraid .
That does make sence paul and by uping the boost it will in turn lean it out a tad so i will see how that goes. Ive also got some more plugs comming ,when i removed them last night possibly no2 was blacker than the rest but they have all been black due to the excessive fuel

Compression check done !

145 on all 4 !

Sounds pretty reasonable,

So lets agree that the cam timing is right !
Its just a case of miss matched components not working together !
Whats my options to make good out of a bad situation without rebuilding the motor!
Im supposed to be a mallory park next friday !!!
Do i bin the rockers for 1.3's and up the boost ! Im i better swapping the cam back !
I no now looking at it my previous spec i wasnt getting the power these engines are capable of but it worked !

Ummm... the Ph2 has an LSA of approx. 110 cam degrees. I would have timed it in at 110.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I am at mallory next Friday also. Hope you can get it sorted in time.
John sleath has always set my motors up, he does know his stuff.

Roy B

deffinatly check the cam timing, its my favorite for being the issue.or at least contributing.

there were different phase 2's, they upped the exh duration at one point, so they might have different LCA's, do you have a spec sheet for the one you have?

just checked both 110 deg LCA

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=11181

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=8343

Edited by Joe C on 9th Jun, 2017.

looking at that data, I'm pretty sure mine is timed in wrong............

Roy fingers crossed.

Joe , its a second hand one i got a good few years ago so not sure ! Sorry

best thing then is stick a DTI on the exhaust valve to see what the lift is,

newer one is approx 390 thou on 1.25's so your looking for about 470 thou or about 490 thou for the older type.

Shit , I was just going to update this thread but just seen your last comment Joe ! I haven't measured to see which cam it was .

Anyway the news is it's hopefully fixed !

The strange thing is the cam timing was 77 degrees!!!!! How did that happen , I have no idea and I'm sure tom will be as baffled as me as to how !
So it's now at 107 -1/2 so close enough .
One of the other problems was I purchased a MED vernier when fitting the cam , there was a normal timing mark on each sprocket but then a big drilling on the cam side , so from memory tom checked both and it seamed to time up with the drilling .
Since speaking to med about it they confirmed they had a batch where the marks were out so had them drilled after , you can tell because the original are black with the anodising and the new one is silver !
The even stranger thing is neither of them line up. !!!!!! Ffs but we have checked and triple checked tdc then on the cam and are happy now we're where it needs to be.
A quick cheeky blast down the road confirms it works better !!

Back to the rollers again

Rick