Can someone tell me the reason I shouldnt boost an NA ?

geee's someone raised the dead..

so you still gonna boost your NA graham, and have 2 TT's?....

 

I waved good bye to my NA about 6 weeks ago. Its TT all the way now !!

I just want it finished. Damn audio system and Immobiliser is holding me up on reassembling the insides now. I got an extra tonne of copper cable in my car now.

I will take a few pics of audio install later today. :zlove:

 

C'mon you slack-arse - get it finished!

 

i always needed 98 octane in my NA... on the lower stuff it would ping going uphiil in too high a gear

 

you would need the ECU, injectors (more air means more fuel), oil squirters arent a must but would help stop the pistons melting when you get on it, biggest one of all is the ummm what do you call the pin things that go through the piston to hold it onto the conrod? anyways, those things are like 1/3 the size in an NA... and will break after enough time on boost... check out tt.net theres a guy on there who races his z, put turbos on his NA and after a while of running fine, or so it seemed, one of those pins broke and the engine was toasted...

ive thought about it too, but the gains you would see wouldnt be that great and your reliabilty would suffer, it would be easier and better long term to sell the NA engine and gear, drop a TT in, or sell the whole NA (to me at a great price coz mines toast ) and buy a TT

 

also forgot, fuel pump (regulator too??) controller for the fuel pump, and brakes... dont want all that power if u cant stop it i think thats about it... although thats just from memory off the top of my head...

 

Brakes are practically the same, the early NA's where 3mm thinner than the TT's. Not worth changing the calipers unless you are going to the much bigger GTR rotor kit.

 

If the following is correct

Does that mean;
TT : 14.7+14.75(boost)=29.4x8.4= 246.96 psi would produce the same power as
NA : 14.7+9(boost)=23.7x10.4=246.48 psi

 

TT will still produce more power.....

because even though both engines will have the same cylinder pressure the TT will have the larger volume of fuel/air mixture in each cylinder.

 

How does that work? The displacement is the same, they have the same stroke. You would think that a combustion occuring at the same pressure (combination of boost and CR) would produce the same amount of energy.

Or is it due to the fact that the OVERALL volume in the TT is bigger, even though the swept volume is the same? I think I answered my own question

 

I think you're catching on Chrispy.....

even though the actual cylinder capacity is the same, the fact that the TT has an extra half bar of fuel/air rammed into it makes the cylinder volume larger.

 

SO how do you calculate them on an even scale?

?

 

You can't easily... given that even though the static compression is higher, that doesn't mean more air is flowing into the engine, nor more fuel. In fact, when you increase the compression you also lower the cylinder volume. This will decrease the amount of air flowing into the engine on the intake stroke. The higher compression just means the air is more concentrated in the area of combustion... this will increase power a bit, but no where near as much as the extra air flowing into the engine from forced induction.

 

since it's forced induction, once the turbos spool up and force air into cylinder rather than have the cylinders suck air into them, wouldn't the volume of air be proportional to the cylinder volume?
hypothetically speaking, if the volume of tt cylinder is 500cc due to lower compression ratio as opposed to na cylinder volume which is 400cc (hypothetically), wouldn't the na cylinder allow less air in under x psi of boost due to smaller volume which would equal to roughly the same cylinder pressure under compression as tt under compression?

 

CR/Volume

The changes in volume versus compression ratio are generally not that dramatic. The piston moves up all the way to the top of the bore and there is very little physical space left after the compression stroke. A very small overall volume change will make a reasonably large change in compression ratio. This is why when you deck the heads/block you generally need to put in a thicker head gasket.

 

that was my next question

How much could you reduce the compression of a NA engine by using thick head gaskets? Could you go as far as dropping from say 10.5:1 down to 9.5:1. Would this drop require a gasket thickness of OEM*1.1?

 

Answer

Sorry about the imperial measurements... was using a calculator that was in imperial

This is making a few likely incorrect assumptions (combusion chamber volume and piston top volume) but should give you a reasonable idea

bore 3.43 in
stroke 3.27 in
gasket 0.04 in
deck height 0.035 in
piston top volume 20 cc
combustion chamber 20.75 cc
= static CR of 10.5:1

Changing the gasket to 0.08 in moves the CR to 9.5:1

Which is ~2mm. Double the size of the stock 1mm gasket.

 

so the cheap way

to reduce compression, yes or no?

This would mean with a 3mm gasket (huge) you could run same boost on an na engine just as safe as the same boost on a TT one.

 

i think you would be better off with a decompresison relief in the piston crown. or hog a bit out of the combustion chambers

 

3mm is a very thick gasket... You might run into problems at that thickness with anything but a metal gasket. The best thing to do is change the pistons and take some material off them (or just change to aftermarket pistons where you can select how much valve/compression relief you have on them)