I have been following forum members desires to turbo/supercharge the TB4.2 motors, either whilst on petrol, LPG or dual fuel. Normally, factory petrol motors that are boosted have a factory lowered compression ratio. I think this is done to compensate when the motor is on full boost and causes less stress on the motor.
Q. Are there any differences in the cylinder head design of the 4500 and 4200 motors?
Are they interchangable?
Does it makeit any difference to the compression ratio if you swap heads.
For eg, years ago I had a 351 C and put 302 C heads on which gave me more compression due to the smaller combustion chamber of the 302 heads.
The VL turbo also had a lower compression ratio over the normally aspirated EFI version.
Any ideas.
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4500 and 4200 Nissan Heads
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A speed camera would have prevented that!
I was once told that they used to put petrol heads on the diesel blocks on gemini's when they hung turbos off htem. The bottom end strength of the diesel block handled the stress much better than the petrols.
I have never seen this done, but One old bloke I know swears that he did it once.
I have never seen this done, but One old bloke I know swears that he did it once.
My Cruiser is Environmentally Friendly.
It runs on recycled Dinosaurs.
It runs on recycled Dinosaurs.
Re: 4500 and 4200 Nissan Heads
I don't see a need to do this as the standard tb42 carby engine has somthing like 8.3.1 compression.RoadNazi wrote:I have been following forum members desires to turbo/supercharge the TB4.2 motors, either whilst on petrol, LPG or dual fuel. Normally, factory petrol motors that are boosted have a factory lowered compression ratio. I think this is done to compensate when the motor is on full boost and causes less stress on the motor.
Q. Are there any differences in the cylinder head design of the 4500 and 4200 motors?
Are they interchangable?
Does it makeit any difference to the compression ratio if you swap heads.
For eg, years ago I had a 351 C and put 302 C heads on which gave me more compression due to the smaller combustion chamber of the 302 heads.
The VL turbo also had a lower compression ratio over the normally aspirated EFI version.
Any ideas.
this engine beggs for boost.
Reptile fabrication.
www.agroautomotive.net
www.agroautomotive.net
You can turbocharge almost any naturally aspirated engine without lowering the compression ratio - if you limit the boost low enough.
Many years ago a rough rule of thumb for petrol engines (running 96 octane Super) was Comp Ratio + half boost (in PSI) = 14. So a 9:1 compression could run up to 10psi boost - if you're careful.
Add things such as water/methanol injection or intercooling and you could go higher. With modern engine management systems and 98 octane fuel you could probably also go higher. With LPG you turn off the heater during boost and the expanding gas provides the intake cooling.
8.3:1 and 8psi will give a handy performance increase, with minimal stuffing around and relatively low stress levels. Select a housing aimed at providing low rpm boost and it'll work well off-road, and minimise the need to downshift on the highway.
Who needs 20psi anyway?
Scott
Many years ago a rough rule of thumb for petrol engines (running 96 octane Super) was Comp Ratio + half boost (in PSI) = 14. So a 9:1 compression could run up to 10psi boost - if you're careful.
Add things such as water/methanol injection or intercooling and you could go higher. With modern engine management systems and 98 octane fuel you could probably also go higher. With LPG you turn off the heater during boost and the expanding gas provides the intake cooling.
8.3:1 and 8psi will give a handy performance increase, with minimal stuffing around and relatively low stress levels. Select a housing aimed at providing low rpm boost and it'll work well off-road, and minimise the need to downshift on the highway.
Who needs 20psi anyway?
Scott
I am afraid I can't answer your question in a definite way but based on the following it sounds like (a) they might be interchangeable but (b) wouldn't make a difference to compression ratio:
Nissan Patrol ST 4800
There's an old adage that says, 'don't fix it unless it's broken'. Well, it was broken and now it's been fixed. We're talking about the petrol GU Patrol. And, no it wasn't broken in as much as it wouldn't go, but in terms of being a good thing, it was indeed broken.
Compared to the GQ, the GU beefed up by around 200kg (depending on the model) thanks to a bigger body, more kit and concessions to safety, noise suppression and comfort. At the same time the simple expediency of a 3.5mm bore increase saw the long-serving TB42 grow from 4.2 to 4.5 litres to become the TB45E. With the help of other changes including new inlet plumbing, the power and torque figures grew from 125kW at 4200rpm and 325Nm at 2800rpm to 145kW at 4400rpm and 350Nm at 3600rpm.
Then to the 4.8...
Nissan's answer is a complete makeover of its long-serving in-line six. First up the stroke has been lengthened from 96mm to 102mm and with the unchanged 99.5mm bore, capacity goes to 4.8 litres. More importantly there's an all-new double-overhead cam, 24-valve cylinder head complete with variable valve timing on the inlet side replacing the old and archaic 12-valve cylinder head and its pushrod actuation.
http://www.overlander.com.au/pg/vehicle ... php?id=190
I can't vouch for its accuracy but I thought it might help you a bit.
Hopefully someone has some actual practical experience on this topic.
Jason
Nissan Patrol ST 4800
There's an old adage that says, 'don't fix it unless it's broken'. Well, it was broken and now it's been fixed. We're talking about the petrol GU Patrol. And, no it wasn't broken in as much as it wouldn't go, but in terms of being a good thing, it was indeed broken.
Compared to the GQ, the GU beefed up by around 200kg (depending on the model) thanks to a bigger body, more kit and concessions to safety, noise suppression and comfort. At the same time the simple expediency of a 3.5mm bore increase saw the long-serving TB42 grow from 4.2 to 4.5 litres to become the TB45E. With the help of other changes including new inlet plumbing, the power and torque figures grew from 125kW at 4200rpm and 325Nm at 2800rpm to 145kW at 4400rpm and 350Nm at 3600rpm.
Then to the 4.8...
Nissan's answer is a complete makeover of its long-serving in-line six. First up the stroke has been lengthened from 96mm to 102mm and with the unchanged 99.5mm bore, capacity goes to 4.8 litres. More importantly there's an all-new double-overhead cam, 24-valve cylinder head complete with variable valve timing on the inlet side replacing the old and archaic 12-valve cylinder head and its pushrod actuation.
http://www.overlander.com.au/pg/vehicle ... php?id=190
I can't vouch for its accuracy but I thought it might help you a bit.
Hopefully someone has some actual practical experience on this topic.
Jason
This is not legal advice.
So the 4500 and the 4800 may only be "stroker" versions of the TB42 engine. If the heads did interchange, than would the cranks etc. interchange? Is the 4800 cam still gear driven? I too would like some more inches!
Last edited by BowTieGQ on Sat Aug 06, 2005 10:40 am, edited 1 time in total.
A speed camera would have prevented that!
Thanks Chimpboy...
I am sure someone would know whether the heads fit, and what changes they make or don't make. For eg if they are interchangeable and they raise the compression, then that would be a easy increase in HP, couple that with a cam or extractors and you have a fairly simple mod.
Also does the 4500 head flow better, bigger valves etc..feel free for anyone to jump on board.
I am sure someone would know whether the heads fit, and what changes they make or don't make. For eg if they are interchangeable and they raise the compression, then that would be a easy increase in HP, couple that with a cam or extractors and you have a fairly simple mod.
Also does the 4500 head flow better, bigger valves etc..feel free for anyone to jump on board.
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