.... you do need to port out the valve port to suit don't you?

Looking into 33mm valves for my engine, to replace the oem 29mm ones, but not sure if this will involve me having to send my head away for further work? It's already been fettled by Jabba in the porting department, but it's using the original valve system.

there is no point in fitting bigger valves in a hole designed for a smaller valve

so yes, the valve hole needs making bigger, probably requiring a new valve seat

assuming this can all be done of course and there is enough metal to machine out

Is it a diesel?, if it is, it would be a waste of time and money. No fuel passes the inlet valves, only air, so unless you have over fueling due to larger injectors and insufficient air to match, there is no point.

:iagree: and as Ric says, you need metal between the valve seats before you can widen ports and seats anyway.

Is it a diesel?, if it is, it would be a waste of time and money. No fuel passes the inlet valves, only air, so unless you have over fueling due to larger injectors and insufficient air to match, there is no point.

this is the car thats trying to hit 300+ bhp,it has bigger everything,and flow through the 8v head is a problem,trouble is jason you are barking up the wrong tree,you just can't get the bigger inlet valves in,its lumpier cams you will have to go with,but all the cams available seem to suffer excessive wear

trouble is jason you are barking up the wrong tree,you just need to drop a petrol engine in there

Corrected

this is the car thats trying to hit 300+ bhp,it has bigger everything,and flow through the 8v head is a problem,trouble is jason you are barking up the wrong tree,you just can't get the bigger inlet valves in,its lumpier cams you will have to go with,but all the cams available seem to suffer excessive wear

Does Giggle Gas work with diesels? I'm sure Wizards of NOS will know.

Does Giggle Gas work with diesels? I'm sure Wizards of NOS will know.

jason has allready been down that road,it didn't seem to do a lot iirc,and then he ran lpg/nitrus and derv and i'm not sure what all that did either:rofl:

I've looked into a better cam. Might well order one and fit it whilst the car is off the road. Guess I can leave the valves as stock, but they are limiting.

You'd grind the seat area to suite the larger valve, then grind/lap out the hole in the middle so that the seat/valve contact area is similar to factory spec. Or with tuned engines, slightly slimmer. The throat area of the port underneath the seat would be smoothed into the larger entry hole to avoid ridges, sharp edges.

Was going to say 33mm is big. Then read of some nut running 38/35! :eek:

J.

But as has already been said, only air (and exhaust) passes through the valves in a diesel, and diesels of course are designed run on excess air as it is. So unless there are major issues with overfuelling, bigger valves won't help. Changing the cam so they open for longer might work, would be just the same, surely?

I'm no expert, but I reckon that leaves a change of bore and/or stroke as the only options if the block's to be kept. Stroke length probably can't be touched either, actually, since diesel burns so slowly and therefore expecting the piston to move even further per stroke would (AIUI) allow more power at the bottom end but reduce the red-line. And a bore-out would appear to be out of the question too, if the third-from-bottom post here is anything to go by...

Or Jason could try a petrol engine, as Andrew so helpfully pointed out!

Whatever happens, :popcorn:

With a heavily tuned derv, the biggest problem is getting rid of the exhaust gases.

In that case, bigger ports would help and opening up the inlets to a similar size won't hurt either.

With a heavily tuned derv, the biggest problem is getting rid of the exhaust gases.

In that case, bigger ports would help and opening up the inlets to a similar size won't hurt either.

Does that lead to a chicken-and-egg issue with the turbo, then?

Actually, I'm not sure the Seat WTCC cars manage 300bhp, and they're running the 2.0 block, not the 1.9. Where they score is having way more torque than the 2.0l petrol atmos they're competing against.

I think the way forward to get more power if you have a given engine running the usual "lean everywhere" diesel cycle might be to increase the peak mass flow rate of the injectors so you can get the fuel in faster, and maybe go from (figures for illustration only) 1x 200cm^3/sec injector per cylinder to 2x125cm^3/sec injectors per cylinder so you get a more even fill faster.

262bhp from the 2.0 block, according to this. Last I heard, Jason was on 240-something... :ne_nau:

No more torque than you could achieve from a simple remap (330lb-ft), so other than the 16v head allowing higher revs, I don't see where the extra ponies could come from, really...

The issue with the exhaust, is that you've got part combusted and post combusted fuel that isn't out of the chamber as so when you get the fresh charge it can't burn properly because some of the air in there is used to burn the left over mess. Add the EGR system into this and it gets even worse.

Yes a derv usually runs with an excess of air, but you can see when even this amount of air isn't enough to burn the fuel completely in a combustion cycle. Derv isn't a fast burning fuel, hence you can't rev it too highly because it won't have finished combustion at higher revs.

You can't IIRC get over the burning all the fuel in the time available issue, short messing with they cylinders or having an optimised spray pattern from the injectors such that the derv is sprayed in a finer mist.

The larger exhaust ports and removing the EGR function however will allow the engine to have a more empty cylinder to start with and hence more clean air in the combustion mix.

The wider exhaust ports then has the effect of increasing the amount of exhaust out, so increasing the effect on the turbo and so increasing the air compressed in even further. This potentially can increase the fuel that can be injected, but on modern engines that is down to the ECU map.

However when widening the ports, in theory you could end up lowering the gas pressure to the turbo then you would have less air compressed into the engine in a given time, however a wider pipe could do the same thing. The ECU can however be mapped to deal with this by increasing boost, assuming the turbo can deliver it.

Once you get to the top end on dervs, it starts to get quite complicated as to how to get the fuel to actually burn in the time given.

May I suggest liquid oxygen tank, for injection at high revs (Not serious btw)

262bhp from the 2.0 block, according to this. Last I heard, Jason was on 240-something... :ne_nau:

No more torque than you could achieve from a simple remap (330lb-ft), so other than the 16v head allowing higher revs, I don't see where the extra ponies could come from, really...

Indeed it's the 16v head, which means a touch less torque lower down, but the engine can be effective further up the rev band and so keep the power for longer.

Again that's because it can get rid of the exhaust gases at the higher engine revs.

May I suggest liquid oxygen tank, for injection at high revs (Not serious btw)

Thanks for the explanation on the exhaust gas thing, but would LOX really be any different to nitrous...???

Thanks for the explanation on the exhaust gas thing, but would LOX really be any different to nitrous...???

It's none bonded (well to other oxygen molecules) and likes to react and causes things that are on fire to burn a lot more intensely.

NOx on the other hand, has to break the Nitrogen to Oxygen bond before it can react.

Basically to make NOX react requires more energy in to break the initial bonds than just oxygen that isn't bonded to a Nitrogen.

EDIT:

I should note I'm assuming O=O and N=N=O

Now if you could somehow bottle singlet oxygen and it didn't react on the way into the chamber you would be onto something.

Edited 13 October, 200916 yr by cheezemonkhai

In the simplest terms, you'd need two moles of nitrous for every mole of LOX, however the activation energy for the 2N20 -> 2N2 + O2 reaction is quite low and you get a shedload of energy released plus a 50% increase in the number of moles of gas when the decomposition occurs, which provides an effective expansive force before any combustion takes place.

In terms of 'liking to react', both gases are powerful oxidising agents, however the index of flammability of fuels in nitrous will be higher than that for oxygen as you say, since the nitrogen molecules produced clearly do not support combustion.

The fact that the boiling point of nitrous is around 100K higher than that of oxygen means that it must be stored at much higher pressures in liquid form, and so a thicker (heavier) tank would be required, as well as a heat exchanger (more weight) to prevent the fuel system freezing as the LOX expands.

I suspect I'm taking this far too seriously, however...

In the simplest terms, you'd need two moles of nitrous for every mole of LOX, however the activation energy for the 2N20 -> 2N2 + O2 reaction is quite low and you get a shedload of energy released plus a 50% increase in the number of moles of gas when the decomposition occurs, which provides an effective expansive force before any combustion takes place.

In terms of 'liking to react', both gases are powerful oxidising agents, however the index of flammability of fuels in nitrous will be higher than that for oxygen as you say, since the nitrogen molecules produced clearly do not support combustion.

The fact that the boiling point of nitrous is around 100K higher than that of oxygen means that it must be stored at much higher pressures in liquid form, and so a thicker (heavier) tank would be required, as well as a heat exchanger (more weight) to prevent the fuel system freezing as the LOX expands.

I suspect I'm taking this far too seriously, however...

I started to then suggested singlet oxygen :thumbup:

As a generalisation for diesels, as cylinder volume /\, peak revs \/ I think.

I was wondering if part of the issue was getting the advance of the flame front speeded up, hence the idea of using multiple injectors, but this would require some serious research to get beyond "I think it might work".

...singlet oxygen...

Predictive text fail?

Predictive text fail?

:confused:

Singlet oxygen - Wikipedia, the free encyclopedia

Predictive text fail?

Oxygen in a vest?

:confused:

Singlet oxygen - Wikipedia, the free encyclopedia

Ah, apologies for the confusion - I'd not even heard of this particular metastable isomer! But now you come to mention it, it begs the question: why bother?