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PostPosted: 08 Jan 2010 22:27 
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Chook wrote:
matter if you are blowing a ton of unburnt fuel and air directly out the exhaust valve thats open at the same time as the inlet if the turbo is large enough to pump the extra wasted air. . :D


That's what you normally read on US forums.

So what you're saying is that the volumetric efficiency is a lot more than 100% which is what all engine designers put all the effort into getting?

Anyone who's run a turboed N/A motor on race N/A cams knows that they go really well and that it's just a myth that mivec cams are unsuitable for turbos. It even says in the turbo bible that any cam which works well in an N/A situation also works well in a turbo situation and favours the same rev range. Most "turbo cams" are designed to make low down torque much like a US V8 "towing cam"
It's nothing more than bad for business for people who sell aftermarket cams.

Steve

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6G74 mivec bored and stroked to 3.9 litres....Frankenmitsi build.
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PostPosted: 09 Jan 2010 09:47 
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From a purely observational standpoint, when you look at the engine specs that most highly tuned turbo cars run, its never anywhere near the longest durations that are available, I don't recall ever seeing a highly tuned turbo car running 300+ duration cams they seem to peek out at around 286, that includes drag motors which really could care less about things like fuel efficiency or low down torque performance.

I'm sure there will be a cross over point where an increase in boost pressure is more advantageous than increasing the cam duration to get the same amount of air/fuel into the cylinder.

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PostPosted: 09 Jan 2010 12:34 
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magn1t wrote:
Chook wrote:
matter if you are blowing a ton of unburnt fuel and air directly out the exhaust valve thats open at the same time as the inlet if the turbo is large enough to pump the extra wasted air. . :D


That's what you normally read on US forums.

So what you're saying is that the volumetric efficiency is a lot more than 100% which is what all engine designers put all the effort into getting?

Steve


Actually Steve no I wouldn't say that air flowing through the cylinder and directly out the exhaust valve contributes to volumetric efficiency. Thats the exact opposite of efficient, its waste isn't it.
Volumetric efficiency as I understand it for an N/A application is getting as close to or in extreme examples marginally over 100% cylinder filling for the intake charge. For a forced induction application you should be far in excess of 100% cylinder filling as its under pressure. But its still not a volumetrically efficient system if say only 80% of the air being pumped by by the turbo stays in the cylinders as part of the intake charge. With the remaining 20% of air fuel mix flowing directly out the exhaust.

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PostPosted: 09 Jan 2010 13:20 
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It doesn't work like that.
Generally when a turbo motor has higher than atmospheric pressure in the intake manifold, it also has higher than atmospheric pressure in the exhaust manifold, as one rises, so does the other. The presssure differential is pretty much the same whether it's got a turbo or not.

Actual VE, based on % filling is nearly always less than 100%, a turbo just makes in more dense so with respect to atmospheric conditions a turbo will increase VE but with respect to % filling it doesn't. Actually an 11 to 1 motor can have up to 110% VE (combustion chamber space) before any air/fuel comes out of the exhaust unburnt, it's just not going to happen .
It's only for Americans. A 300 degree cam isn't going to idle properly when used with EFI due to reversion, likewise a 300 degree cam won't idle too well with a carby either. Just as well there's a low speed cam to go with it.

Steve

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6G72 mivec Twin TDO5 20Gs up and running.
6G72 mivec bored and stroked to 3.4 litres...Frankenmitsi build
6G74 mivec bored and stroked to 3.9 litres....Frankenmitsi build.
6G75 under construction....4.2 litres bored and stroked.Another Frankenmitsi.


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PostPosted: 12 Jan 2010 17:42 
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zeni-tani wrote:
Im doing this swap too

I got some custom pistons to suit 92 mivec head on a 4g94 block

My mate sent the whole 4g92 head to piston manufacturer :lol:

Ill update you when i finish manufacturing the 4G94 H-Beam forge connecting rods


please keep us updated... ;-) .. it is interesting to see the result.. as so far that i've heard.. most hybrids projects involve 4g93 blocks only ;-).. keep up the good work...

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PostPosted: 09 Feb 2010 11:20 
i dont want to fork out crap load money buy block head and a aftermarket ecu and it not work or make anything.

So if it worth using a 4g94 lump and marry the mivec head to it.

on a slight off topic would a 4g93t head be better???


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PostPosted: 10 Feb 2010 22:32 
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Quote:
most hybrids projects involve 4g93 blocks only


For obvious reasons i went down that road but didnt use that block :D

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PostPosted: 10 Feb 2010 22:46 
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what block did you use???

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PostPosted: 11 Feb 2010 12:53 
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i can see what uve done cause i tried something with few weeks back but something had to be customised. I wont reveal cam just in case its similar to your set up BTW congrats on the 144KW!


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PostPosted: 11 Feb 2010 13:36 
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I dont think Cams held back too many secrets. But its a combination of a lot of good things and not neglecting key areas.

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PostPosted: 11 Feb 2010 14:45 
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And an amazing head porting job! for basically free

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PostPosted: 11 Feb 2010 15:47 
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Chook wrote:
I dont think Cams held back too many secrets. But its a combination of a lot of good things and not neglecting key areas.

Yes correct i can see roughly what has been done

BTW seeing that we are talking about porting the head throw some tips, did you guys just enlarge the intake ports and worked on the valve guides still following the Intake port shape? Extrude hones perhaps, mirror finish combustion chambers and exhaust ports?

Im marely interested on the buttom end setup i think i have this figured out however i must admitt i have not played around with the head that much pretty much been running them stock.


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PostPosted: 11 Feb 2010 16:07 
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DRTDVL wrote:
And an amazing head porting job! for basically free


Yeah I remember seeing the head after the job was done. It had been well and truly worked over. It certainly did the trick on the dyno.

From what I saw of the head there are BIG gains to be made over the standard one. Correct me if I'm wrong Heath but the big focus was on getting the ports to line up correctly with the valve seats.

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PostPosted: 11 Feb 2010 16:23 
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Chook wrote:
DRTDVL wrote:
And an amazing head porting job! for basically free


Yeah I remember seeing the head after the job was done. It had been well and truly worked over. It certainly did the trick on the dyno.

From what I saw of the head there are BIG gains to be made over the standard one. Correct me if I'm wrong Heath but the big focus was on getting the ports to line up correctly with the valve seats.

Chook i have your old head remember :)

Anyway are they that far out, like i said i never opened it up bear


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PostPosted: 11 Feb 2010 16:28 
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Chook wrote:
Yeah I remember seeing the head after the job was done. It had been well and truly worked over. It certainly did the trick on the dyno.

From what I saw of the head there are BIG gains to be made over the standard one. Correct me if I'm wrong Heath but the big focus was on getting the ports to line up correctly with the valve seats.


That head was ported to match the cam spec's he provided. It's an aggressive port job.

There where a few things that where done to tidy it up. Port wall to Valve seat alignment (was out by a few mm to 5mm if i remember correctly), The chamber had lovely casting pin marks, A LOT of material was removed to match the manifold to the head. A lot of time was spent looking to improve the velocity of the head.

Cam - your quads - are they matched to your ports?

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