Turbo cylinder head advice

Road-race engines and ancillaries - general discussion
Testament
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Turbo cylinder head advice

Post by Testament »

I'm in the process of building a turbocharged 8v twin cam, based off an argenta 2L engine. The idea is to build the engine properly to take high boost and give the turbocharged japanese imports a run for their money come dyno, dragstrip or racetrack. But things started a bit sadly, meaning to "do things properly" I took the head to a "so called" "race engine builder" on advice of someone in top level motorsport (in NZ). The head was to be ported with 44mm/38mm valves, bronze valve guides etc. after many months and too many dollars I found he was a total cowboy and that I would probably have to do things myself to get them done right.

So after all that I had a clean head with a flat surface, bronze guides and the 44mm and 38mm Ferrea stainless valves. After a lot of work (mostly lapping by hand) I got a good seating on the valves (they were waaaay out), but they could probably still do with a bottom cut and maybe a top cut, but there is not much meat in the seats for a top cut. I realize it might even be best to just get new seats put in. So far I've roughed out the ports a little to match the gaskets/manifolds (croma turbo inlet, custom exhaust.) but they could probably do with some more finishing. I also polished the combustion chambers and CC'ed them (all were 50cc +/- 0.5cc). The ports are 35mm-33mm at present, I've taken off as little as possible so far realizing I can't put any back.

This all got put aside for my final year of university, but I am now working at a power station and have access to a fully equipped machine shop (and a proper income helps), and the help of several competent machinists (If I play my cards right).

Any advice would be greatly appreciated.

Thanks, Tom

more engine specifications
130TC cams
Adjustable camwheels
Forged pistons 7.5:1
Croma turbo inlet manifold
Intercooler approx. 450mmx300mmx65mm
IHI RHC6 Turbocharger
52mm inlet on compressor wheel
59mm exducer on turbine, 0.79 A/R
Intended boost level 20psi+
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a view from work
a view from work
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Wallace
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Post by Wallace »

The only advice I can think of is to use Fiat sodium cooled exhaust valves.
I think they were fitted on all the "blown" twin cams - Volumex and turbo -and given the cost of them I don't think Fiat would have fitted them if they weren't necessary. They're about 8 times the price of a "normal" one !!

I has a Delta Turbo head on my turbocharged Montecarlo engine with these valves fitted - and everything was fine for the 20 thousand miles or so that I ran it.
WALLACE
Guy Croft
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Post by Guy Croft »

Hi

Some nice pictures, thanks, I like the scenery! Here is some prelim advice:

1. I asssume you have had bigger seats fitted. The bigger valves definitely need them, you cannot (just for the record) fit 44/38 on the head original 42/26 valved head. I imagine you know this.

2. Contact faces need to be 1.5-2mm. Thinner seats inlet will give poor flow and less than 1.5 ex may burn, esp with non sodium cooled valves.

3. I note you have bronze guides boths sides, good. I accept that it is very expensive to have s/c valves made at 38mm; yes the OE are expensive even at 36mm, about ‚£45 each in the UK. Because the ex valves are not s/c I would not run high boost, the high temp may distort them. You need to open up the ex ports with the bigger valves, if you have not already, esp around the guide region, otherwise you'll have a high flow seat/throat restricted by a small port. I am not sure you really needed 38mm valves on the ex, I think, with the right porting on the ex side you would comfortably have enough ex flow. The TC has a very high E/I (ex-inlet) flow ratio - 75% + from memory - if ported right, even with 44/36 valves - more than enough for the turbo application.

3. A boost of 20psi plus is too much for a production head gasket, 17psi tops, in fact you may struggle to get any gasket strong enough for that, Spesso may do one if you can get it. Spesso only do runs of I think 6 off at a time and there if no-one has stock is always a long wait.

4. I would not do it that way anyhow. I'd open out the ports to 35mm thru, this will let it flow a lot more, esp bearing in mind that it has big inlets. This will give more power for same boost, and thus you can run a lower level of boost which I would set at 12-14psi and you should hit 300bhp comfortably. I think you should test this out and get some exp before going anywhere higher. Don't be impressed by huge numbers. Most people have never driven with that much power and the huge torque that goes with it, far less know the difference between 300 and 400.

5. Do not use the 130TC ex cam, use a cam with lower lift - 8V 1600 or 2 liter Turbo model ex cam 8.6mm. This will give a much more driveable characteristic. You don't need so much lift with turbo models, never run like-for-like cams.

6. As for cooling, you need to keep the motor temp down to 75deg C and the inlet charge temp down to 45 deg C and you must run an aftermarket mappable ECU.

7. The ex system wants to be a single large capacity straight thru design. Turbos don't need half the muffling of n/a units and too much will create back-pressure downstream of the turbine.

I hope this helps.

GC
Testament
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Post by Testament »

Thanks Guy,
Engine control will be fully mapped fuel and ignition. The block is going to get o-rings(wire), and either a croma turbo gasket, or I have seen that cometic do a MLS 16v integrale gasket that may be the bussiness if it as good as their gaskets for other engines. Can a 16v gasket be made to fit an 8v if holes are made for the extra oil galleries?

I am also wondering if it is worth installing oil sprayers under the pistons, the old style rods do have the two small holes that may have the same effect to a small extent, but do not aim directly at the piston.
Guy Croft
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Post by Guy Croft »

I wouldn't bother with oil sprays, you'll have enough to do getting it set up and running right, save that for the next one. I have run plenty of engines like that without.
The gasket has different coolant holes inlet and ex, you must not run a late generation gasket with the early head, it will detonate.

GC
Wallace
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Post by Wallace »

Oil sprays can be done - but the crank and rods are a very tight fit inside the block. Barry Waterhouse fiited ones to my engine a few years ago - but if you actually follow the line of the jets, half the time they oil would hit the con rod !!

Hence the Mrk 2 versions in the photograph ! This is the old block - the far one is a just a pattern to see if the idea's good. Barry's ones were just simple jets - they didn't have the copper bends on them. I think they were one way brake bleed valves !! The jets were turned up on the lathe and will open at a specific oil pressure - 18 psi. This is so they won't bleed down the oil pressure at tickover where you don't need the cooling effect of the oil.

I'd like to say the holes in the new engine block were accurately drilled on the mill - but they weren't as the mill wasn't big enough and I couldn't get my head around how to work out what angle to drill them at. So I'll come clean and admit I did them carefully with a wheel brace ! The major problem is starting them as you're drilling into the oil grove - the trick is to use a carbide burr to create the first hole. I wouldn't recomend belting a cast iron block with a centre punch !!! They were cut to the final size (7mm) with a reamer. I do have some photo's but not on me.


When they're finally installed, they will be held in position by a mixture of loctite and a small clip. Being copper, they will be tweaked so the jet really gets to where it needs to be. And being copper if they fatigue off, they won't bust up the engine !

Note also the crank scrapper ..(sorry about the focus . .or lack of). !
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WALLACE
Guy Croft
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Post by Guy Croft »

Very nice, Wallace,

your tube solution is similar to the brass assemblies we worked with at Brian Hart on the V8, 10 F1 engines, his were held in by a circlip, sprayed both bores from the crancase saddle, and very neat but wow, fiddly.

This is one I did last year. The compound angle of the drilling and boring was all set out on cad first, the machining op is not easy at all. The sprays are directed at the inlet side of the piston. The little spray valve is a light interference fit in the counterbore and has a modest clearance under the bearing.
The only post-machining op reqd is a bit of dressing to the crankcase. The valve (as you have, and minde) prevent the system from robbing oil pressure on start.

GC
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sumplug
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Post by sumplug »

one question. why is the engine running such a low static compression. with a boost control box, you could run up to 9:1-1 compression without any detonation. would make the engine more tractable at the bottom end. what you think Guy?
Testament
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Post by Testament »

Boost control box? you are going to need to explain what you mean. If you mean an electronic boost controller I don't understand how it would allow you to run higher compression. They are usually installed to reduce turbo lag by keeping the wastegate completely shut untill the desired boost level is reached.

The low compression ratio is to allow for the large turbo running at high boost, for a higher peak output. I know this will make the engine a slug off boost, but I'm willing to accept that for this engine.

Very nice work on the oil sprays guys, but I think I will go with as guy suggested. I can see the wisdom in getting the thing going and leaving some things for version 2 if I get there.

Tom
Guy Croft
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Post by Guy Croft »

The question of how high the static CR can be taken for given boost/engine/fuel is totally a question of test and experience, or advance software analysis (that only the wealthiest universities and development facilities or companies can afford).

For us - there are just no, no, no guaranteed formulas for it. Sorry. Believe me, I'd tell you if there were, I have watched for years.

Unless you want to 'blow the thing to bits' you always run the lowest static (not the highest) CR you can get away with. If you want high CR don't pressure-charge the engine, period. Turbo gasoline engines will always have a compromise power response because you are effectively bolting a 'gas-turbine' to a steam engine running on gasoline and the thermodynamic behaviour of the two could not be more different. See also:

http://guy-croft.com/viewtopic.php?t=164


GC
sumplug
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Post by sumplug »

Boost control box like SAAB APC, allows a higher boost by using a knock sensor to determine detonation, as soon as it feels it, it knocks the timing back and opens the wastegate! a pretty much foolproof system. Its also easy to have it dash adjustable too. So in theory, allows the ability to use higher static compression. What we have not discussed, is dynamic compression as each engine is different.!! :)
Guy Croft
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Post by Guy Croft »

Hi

Nope, sorry Andy, all attempts to produce foolproof products only seem to bring out a new type of fool.

As for detecting the knock, never mind the black box, all that counts the information sensor on the engine. No-one has developed any system of any kind - yet - that will bolt on to any engine to find just the really big pressure peaks. I doubt if anyone ever will.

I mean - no-one, be careful.


GC
sumplug
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Post by sumplug »

Hmmmmmm.......
My Turbocharging knowledge is sadly limited. Never really got into them as ive seen so many engines recked by them [Uno Turbo for example]. But, to put a pump onto another pump without considering all, you are asking for trouble. So you reckon on keeping to a safe limit for compression? What is considered a safe limit?? :)
SirYun
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Post by SirYun »

it seems that it is possible to use high boost and high (static) CR under certain circumstances.

Endyn claims (but i never seen one up close) a 11+ CR with 22psi boost on a Honda.

but who knows how many grenades the build before they got that working. So i would stick to low CR :wink:

http://www.theoldone.com/articles/Larry ... _Civic.htm

the workmansship looks good as far as i can tell by looking at the pictures
Joost M. Riphagen
Testament
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Post by Testament »

SirYun, What fuel is he using though? It makes a big difference if you can run higher octane and tune for it.

This APC unit, may work fine on a fairly standard engine, but knock on a highly bosted engine can mean oily paperweights in no time at all.
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