who builds the best engine for motorsport in the uk

My rally Pulsar runs a fuel pressure gauge, a lambda reader and an injector pulse width reader on the dash. Being turboed its good to know that the mixture isnt going lean

 

Also runs a fuel swirl pot and a second in line fuel pump to avoid surge. Something else that may cause a lean run condition

 

Sounds like a very high c.r relative to the cams going by those pressures...somewhere around 13:1+...it's sounds like it's detonation damage on the head..the low pressure and power drop off maybe ring damage due to excessive cylinder pressures.

1604's are hydraulic profiles unless they've been shimed tight or the cams have been ground as a solid lifter version.

A look at the map will give an idea how good/bad it is and if it could be a likely cause, though Northhampton Motorsport have a lot of experience.

A fuel system pressure check as Danny suggested would be a good idea.

 

Anyone know what CC the combustion chambers should be when running 12.4 CR

 

There's some useful data here which should help you:

http://www.clubgti.com/forum/showthread.php?t=245146

 

Based on the std bore and stroke figures of 82.5 x 92.8 giving 1984cc engine capacity.

Individual cylinder CC = 496cc

12.4:1 CR would require a clearance volume of 43.5cc.

NB: This is the clearance volume, not the head combustion chamber volume. This is because the pistons are intruding into the head combustion chamber volume. Thus reducing it's volume.

 

Alternative way to CHECK C.R. of an engine.

@ 290PSI cylinder pressure during cranking *edit looks high but...

The weight of the air pressing on you/me is ~ 14.7psi at sea level.

Add a bit of negative pressure as the piston sweeps down the bore and this air will attempt to fill the cylinders by moving from an area of higher pressure to an area of lower pressure, when you crank over the engine. At BDC the air should be at 14.7psi sea level

Let's say your engine has been built to deliver 12.4:1 compression and assume the cylinders achieve 100% VE during ( it never will) cranking rpm of >300rpm the theoretic gauge reading should be = (CR^1.3*14.7*2/3)-14.7 ~ si at sea level.
The cam timing events, pumping losses from throttling, port shape, low flow and ring leakage at cranking speeds means this value would be reduced in reality. So for a very overlapped cam factor in 0.85.

Here is a table summarising typical pressures derived if the CR is known.

The crude assumptions are:
The cranking speed is consistent 250rpm for 15 cycles
The cylinder wall temps are an ambient 20C
Cylinder filling is ~90% after 15cycles
We are at sea level
The gauge measurement is assumed to be correct.
Cylinder wall oil film is not excessive

MG = Gauge Measurement (psi)
AMP = Ambient pressure Sea level = 14.7psi
VE = Cr Volumetric Efficiency for non standard cam (90%)
Pressure Gauge = CR^1.3X14.7X2/3XVE
where 1.3 = specific heat ratio for air methane mix (1.4 for pure air)

Estimated Gauge Measurement (psi) nonstd cam	Known Compression ratio :1
255	14
230	13
216	12.4
206	12
183	11.5
161	10.5

This is just a crude check and does not substitute determining CR by burette CCing.

Regarding the engine state when opened and the conclusions?
There are many reasons this can happen and engine calibration, if done in good faith with resonable hardware is not the first place I would go regarding failure. Futher analysis would be required by a suitably qualified professional.
There is also a difference between P.I. and det regarding failure...

On engine builders I would also say, from a logistical point, bung something in the car to carry on in the short term and get whoever is deemed to build the best one to your spec, when they have space.

 

I tried it 4 times and got the same reading , so went out and bought another compression tester , a different make , and got the same readings again , 4 times , so yes my gauge (s) must be wrong !

 

Here are some pictures of the damage to the head , I have been in touch with someone who can build it up with weld and machine it back , he says it looks as though some valve seats will probably need to come out to do it properly







I'll take some pics of the damage to the pistons tomorrow

 

That would be great.

We looking at the damage on cylinder 2 squish pad area?

 

Ignore my previous comment. I have updated the table and formula and this crude calculation now reflects data in the direction of the original information you posted.

290PSI may look high but it only takes excessive oil film and so on to bump the number up like this.

Apologies for the first set of information.

 

I mentioned oil being the culprit for the high reading earlier in the thread.

Anyway , took a couple of pics of the pistons

 

Yes. Saw that about the oil.

Piston 2 started to melt. May have suffered from pre-ignition in this area ( end gas getting very hot and self combusting). If you have not already, I would check the injectors, particular #2 to ensure it is flowing relatively similar to the rest.
Pictures not clear if they were any signs of a similar nature on the other pistons which would point to a global driver such as the calibration or fuel delivery or rpm sync issues.

Top ring land possibly damaged hence the "low compression" in this cylinder on your test.

 

There appear to be marks halfway down the valve cutouts on this piston (no 3). Looks like what you would see when the valves were contacting this area. These marks are not visible on the other piston from what I can see.



Are the inlet valve head diameters std or oversize? If oversize and the valve cutouts in the pistons have not been enlarged to cope with the increased valve head radius then this could happen.

And as Jason (mr hillclimber) mentioned, hydro cams and solid lifters need investigating.

 

There are no contact marks on the pistons or valves , there are some machining marks on them there the cut outs have been machined which is what you can see.

Why would the lifters need investigating ? you can run solid lifters on any cam , you cannot run hydraulic lifters on any cam though , when I spoke to TSR earlier this week they remember supplying the parts for my engine , and they said they supplied a solid lifter kit , i'll see in the next day or 2 as I have to completely strip the head ready to have it welded

 

Stripped the head down this evening to drop it off to the guy who's going to weld it and machine it on my way to the autosports show tomorrow , it does have solid lifters fitted , obviously these will need reshimming for the new cams i'm going to have fitted , don't know what i'm going for yet.

 

Check what valve springs are fitted.... use the correct springs to suit the cams you use.

 

Kent double valve springs with titanium caps

 

interested in your coment about running any hydraulic lifter cam with solid followers. Where did this comment come from?

 

Any cam can be used with solid lifters , why do you think this is a problem ?