Cooling the air intake on a V8

Hello all, sitting on a 3.5 V8 with K&N filters is it true that if i shield the manifold pipes with some sort of lagging and manufacture a plate under the filters allowing cooler air into the filters, this will improve performance? If so any ideas on the lagging?
many thanks in advance
Scrumpy

Yep. Cooler air is more dense than hot air and thus by simple physics contains more Oygen for the same volume.
More Oxygen equals more power because the fuel burns quicker and hotter.
This is how intercoolers work.
The V8 intake manifold sits between the cylinder heads and is heated by the cooling system so wrapping it is not an option.
You could wrap the exhaust manifolds and pipes to try and keep the engine bay temps down but what with I dont know.
Alternatively you could arrange for the intake air to come from outside the engine bay like it does on my TD5 or you could try and install an intercooler set up if you have the room.

Shifty1962 said:

Yep. Cooler air is more dense than hot air and thus by simple physics contains more Oygen for the same volume.
More Oxygen equals more power because the fuel burns quicker and hotter.
This is how intercoolers work.
The V8 intake manifold sits between the cylinder heads and is heated by the cooling system so wrapping it is not an option.
You could wrap the exhaust manifolds and pipes to try and keep the engine bay temps down but what with I dont know.
Alternatively you could arrange for the intake air to come from outside the engine bay like it does on my TD5 or you could try and install an intercooler set up if you have the room.

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Forget the intercooler idea.
It won't do any good and it will cause an obstruction to the air flow.
Turbo systems blow a tad extra to overcome the resistance of the intercooler. NA engines can't do that - all they can do is SUCK.
Beware taking cold air from outside of the engine bay. You may end up with CARB ICING when the conditions favour that, which can be very annoying and downright dangerous too.

The very small temperature reduction you might achieve will make little diffrrence and may even make the power LESS because somewhere between CARB and the spark happening the ATOMISED fuel spray from the carb has to be VAPORISED into gas or it won't ignite properly. This process requires a HEAT energy input, and I feel you should not underestimate the original designer's ability to know that and to design it into the system.

I'm not saying cold air may not be good - but I am saying moderately warmed air may be better in an all-round sort of way.

CharlesY

Was thinking along the lines of an air scoop like some of the American custom cars or dragsters have.
You get a ram-air effect when moving.
Snorkels take air from outside with no probs hence my suggestion but I'm no expert.
In hindsight I agree that the intercooler idea wont work. I forgot my turbo blows at 1.2 bar on full chat. Of course you could always fit a twin turbo system.

Shifty1962 said:

Was thinking along the lines of an air scoop like some of the American custom cars or dragsters have.
You get a ram-air effect when moving.
Snorkels take air from outside with no probs hence my suggestion but I'm no expert.
In hindsight I agree that the intercooler idea wont work. I forgot my turbo blows at 1.2 bar on full chat. Of course you could always fit a twin turbo system.

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If you arrange ram-air into carburettors you will probably melt your pistons and valves due to overheating as a result of a lean mixture.
You MIGHT make a 0.5 bhp improvement in an engine with fuel injection, or you might lose power. Who can say?

The carburettor works BECAUSE there is less pressure on the manifold side of the venturi, than there is on the outside, which causes a low pressure at the venturi which then draws fuel through the jet(s) and into the airstream as an atomised spray. If you ram air at the carb inlet the pressure difference that the designers so carefully arranged WILL be affected for the worse, and you will get more air in, but not enough petrol. The ram air will also pressurise the air in the float-chamber, keeping the fuel level and fuel flow down. Bad bad .... The mixture will go lean, possibly dangerously so. Lean mixtures run HOT ... VERY VERY HOT ..... bye-bye pistons and exhaust valves.

These excellent ideas are re-invented every day.

CharlesY

Thany you all for your responces, i'll take note on them all.
cheers Scrumpy

CharlesY said:

Beware taking cold air from outside of the engine bay. You may end up with CARB ICING when the conditions favour that, which can be very annoying and downright dangerous too.

The very small temperature reduction you might achieve will make little diffrrence and may even make the power LESS because somewhere between CARB and the spark happening the ATOMISED fuel spray from the carb has to be VAPORISED into gas or it won't ignite properly. This process requires a HEAT energy input, and I feel you should not underestimate the original designer's ability to know that and to design it into the system.

I'm not saying cold air may not be good - but I am saying moderately warmed air may be better in an all-round sort of way.

CharlesY

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What a load of bollocks
The V8 can draw in more air at half throttle than can be rammed in travelling at 70mph. Unless you have a very large collector that is
A 998cc motor on full bore can draw in more air than a forward facing carb can collect at race speeds (I have researched and experimented).
That is why modern cars have the air intake piped from the front, to stop the filter drawing in hot dirty air from around the engine bay.
Cool clean air and plenty of it will improve performance, ask any rolling road man.

I toyed with he idea of boxing in the bonnet around the bracing pieces along the top of the engine to collect air from the front and direct it on to the filters, cooling the intake and keeping some of the dirty underbonnet air from being drawn in.
The carbs will ice if they get cold but its the intake charge we are cooling and not the carbs, they get loads of heat in that they sit on top of the V8 heated manifold.

Do it....

landowner said:

What a load of bollocks
The V8 can draw in more air at half throttle than can be rammed in travelling at 70mph. Unless you have a very large collector that is
A 998cc motor on full bore can draw in more air than a forward facing carb can collect at race speeds (I have researched and experimented).
That is why modern cars have the air intake piped from the front, to stop the filter drawing in hot dirty air from around the engine bay.
Cool clean air and plenty of it will improve performance, ask any rolling road man.

I toyed with he idea of boxing in the bonnet around the bracing pieces along the top of the engine to collect air from the front and direct it on to the filters, cooling the intake and keeping some of the dirty underbonnet air from being drawn in.
The carbs will ice if they get cold but its the intake charge we are cooling and not the carbs, they get loads of heat in that they sit on top of the V8 heated manifold.

Do it....

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I bet that man's an expurt.
Ex -a has-been, spurt, a drip under pressure

CharlesY

CharlesY said:

I bet that man's an expurt.
Ex -a has-been, spurt, a drip under pressure

CharlesY

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Sorry but 40 odd years of charging down drag strips , round race tracks and budget street racing have taught me a thing or two, mostly by trial and error and not being able to afford bolt on shiney go faster bits ..

Yeah ... but the man was asking about a bloody V8 landrover running a pair of SU carbs, so don't you bollocks me pal.

What he doesn't need is false encouragement to do a whole lot of stuff that woll cost heaps of time and cash for bugger-all return.

It is more likely a simple change of carb needles would make a difference. I remember fitting a new needle KP I think to my 1500 Maxi (that had been zooped a tad) and just the needle change made a real improvement.

Let's not lead the man up the garden path.

CharlesY

CharlesY said:

Snip ... don't you bollocks me pal.

CharlesY

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Nice friendly debate.

My Yamaha VMAX (1200cc V4) runs way better when its cold out and it's got carbs with ram-air as standard. It dont have a bonnet but power jumps from 165bhp to almost 180bhp (dyno confirmed) when its frosty. I've had the carbs played with by a specialist tuning firm and even they cant make it run as good during the summer as in the winter.
So going on personal experience, and for what its worth, it is my humble opinion that clean cool air will give more power than hot air.

p.s. CharlesY I'm running a 33% mix of hydraulic oil to diesel with no ill effects. Next step is to go the whole hog and try a 50% mix. I'll just put a few gallons in the tank and give it a go and if there's any probs I can top off with DERV and dilute it back to something that works. Got to tow a large caravan about 50 miles for a mate so it will give things a good work out.

Shifty1962 said:

Nice friendly debate.

My Yamaha VMAX (1200cc V4) runs way better when its cold out and it's got carbs with ram-air as standard. It dont have a bonnet but power jumps from 165bhp to almost 180bhp (dyno confirmed) when its frosty. I've had the carbs played with by a specialist tuning firm and even they cant make it run as good during the summer as in the winter.
So going on personal experience, and for what its worth, it is my humble opinion that clean cool air will give more power than hot air.

Very often it will, and especially in HIGH COMPRESSION engines where the heat of compression will cause vaporisation of the petrol thereby helping to cool the pistons. But a V8 LandRover? For all that MIGHT be gained on a cold day, the downsides are too great for me.

p.s. CharlesY I'm running a 33% mix of hydraulic oil to diesel with no ill effects. Next step is to go the whole hog and try a 50% mix. I'll just put a few gallons in the tank and give it a go and if there's any probs I can top off with DERV and dilute it back to something that works. Got to tow a large caravan about 50 miles for a mate so it will give things a good work out.

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Great plan! Watch out for viscosity ... don't let the fuel get too thick or the vanes may fail in the intermediate pump inside the Injection Pump.

A 50-50 mix will probably be fine, and perhaps more in warm weather.

The percentage of Hydraulic oil to Diesel isn't the real point - the point is saving £££££s by getting more litres of free Hydraulic used and less diesel at £1 a litre!

Don't you find the engine runs really smoothly on your fuel mix?

CharlesY

CharlesY said:

Don't you find the engine runs really smoothly on your fuel mix?

CharlesY

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Now you mention it it does run more quietly. I dont get so much of the old diesel rattle when starting from cold and it seems to be more responsive to the throttle although this may just be wishful thinking.
I've saved at least £40 over the past few weeks and I've still got more than 200 litres of the stuff to use. I can get another 250 litres roughly every three months so I'm laughing all the way. Thats £1000 per year in saved fuel costs. Now that I'm more confident that it works I'll be using it almost as fast as I can get hold of it. I'm also told that I can legally use upto 2500 litres of reclaimed oil per year for private fuel use?

Hi there,

It is worth lagging the exhaust manifolds to increase power. I have done this to my 2.5TD firstly to reduce the under hood temperature because these engines don't like to be hot but secondly you get the power increase advantage as well. As the hot air leaves the cylinders and enters the exhaust manifold and pipe it cools rapidly and as it does so it becomes denser and more slower moving holding back the flow of gases out of the cylinder. If you can keep the temperature up in the exhaust manifold and pipe the gases flow out of the engine faster. Lagging the manifold and pipe down to the first junction near the gearbox keeps the exhaust gas heat in. The faster the gases flow out then the more fuel/air can get in and thats where the power increase comes from.

You can get exhaust lagging from motor sport websites. Believe it or not its made of cotton, treated cotton mind you but cotton all the same. You will need stainless steel cable ties about 14 inches long to hold the lagging round the pipework. Fitting it is fiddly as hell with the pipework in place much easier with the pipework off. 40 quids worth was enough for my diesel so you probably would need 2 to 3 times that amount for a V8's pipework but the more you buy the cheaper it gets.

Guys thank you very much for your responces, some for and some against, too the one's for lagging the exhaust manifold i forgot to mention that my car is also LPG as well as the good stuff, is it true that on LPG it runs hotter and will the lagging be to hot for the ex manifold (sorry if it's a really stupid question) i just don't want to break my landy just learn. Are the raised air intake panels on top on the wing any good?
So if LPG does run hotter would it be beneficial to cool the engine bay slightly?
again many many thanks in advance
Scrumpy

I also forgot to mention :doh: yet again that my V8 is also fitted with two Kernlowe elec fans. The question is :blabla: should i set the dial in the eng bay to Neutral or Low to allow the fans to come on, maybe cooling the engine bay
cheers Scrump

scrumpyj said:

I also forgot to mention :doh: yet again that my V8 is also fitted with two Kernlowe elec fans. The question is :blabla: should i set the dial in the eng bay to Neutral or Low to allow the fans to come on, maybe cooling the engine bay
cheers Scrump

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position N is normal not neutral - and is the position to set it at first - if it comes on too soon turn it up and vice versa

if you set it to low it'll be on nearly all of the time when the engine is running

Sorry to upset you CharlesY didn't realise you were the sensitive type, big hug eh :lvhug-035:

thing is..........

If you want to spend money lagging exhaust pipes then Ok but..

Remember that the Land Rover V8 is in an open engine bay and is by no means a high performance engine so I personally wouldn't think that lagging was nesessary, also remember that the heat has to go somewhere and you dont want it sinking back into the exhaust ports and causing the head to heat up which does happen as checked by myself on a mates Pug 205GTI with a laser thermometer. We decided it was better to run without lagging rather than burn the exhaust valves out. Under the bonnet was tightly packed though and enclosed by underbonnet tray.

Regarding the carbs; The old needles are probably worn anyway, especially if running on LPG so I doubt if the mixture will be lean so I wouldn't mess with them if the engine is running Ok, just make sure they are tuned a tad rich for performance rather than a tad lean for emmissions and that they are balanced and have engine oil in the dashpots.

Now I've been told not to use K+N type filters with LPG and I dont know why but will be experimenting with them soon when I get the V8 on the road.

The trouble with the V8 K+N filters is that they sit on top of a hot engine drawing in heated dirty air from the back of the engine bay, a cool air feed would be a good idea and would improve perfomance and economy, trouble is how best to do it.
Ideally the filters should be enclosed and a cold air feed introduced from outside the engine bay, I have several ideas and will be trying them out, one is to box the filters in with the top of the box being the closed bonnet, and introduce a cold air feed from the front of the landy via a boxed section of the underside of the bonnet. Not sure how yet though.
Another idea is a snorkle but that is going to be expensive and I cant afford it.
Another thing is that if you put your K+N's in a box then if you are not careful they will flow no better than a standard filter so pointless exercise.

I thought of using the wing mounted heater intakes but they are not that big and restricted by grills.

A chav bonnet scoop is out because it might have to be too far back on the bonnet where the air is very slow moving due to the steep rake of the windscreen, this would be a good place for an extractor vent though to cool the engine bay. I keep forgetting that the land rover is working hardest when it isnt going very fast so you would need fans to get he heat out rather than relying on air flow.

What I'm going to do with mine for the moment is to make sure that the ignition system is in good order and timed propperly, I'm going to balance and tune the carbs, make sure the engine runs at the right temperature and protect the air filters from hot dirty air. That's about the limit of what anyone can do to improve performance without changing anything. Dont forget that if you change anything then it effects something else and you can end up spending loads of money and ending up with a dog of a motor that is no better that what you started with.

Dont know much about LPG so I'm going to get it checked by someone who does so its safe and running efficiently.

I've got my dizzy marked so as I can advance it for LPG and then put it back for petrol, this worked great when I was on the road last time and there was no noticable difference in performance on gas.

Any tips on the LPG side would be welcome, the petrol side especially as mine has carbs and no ECU, is a doddle.

So we are saying yes to cold air feeds and dont spend money on go faster shiney bits. Get the timing right by rolling road if you can or by an expert, the manuals just give a rough guide and can be way out when an engines bits and bobs are worn. Get the carbs set up and it'll go like a rocket.

Great responces guys thanks
Has anyone used the raised wing top air vents? Anygood?
If so i was thinking of possibly redirecting from under the vents and pointing them towards the filters, what do you guys think?
cheers Scrump

scrumpyj said:

Great responces guys thanks
Has anyone used the raised wing top air vents? Anygood?
If so i was thinking of possibly redirecting from under the vents and pointing them towards the filters, what do you guys think?
cheers Scrump

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Sounds like a plan.
I think they are meant to be used for the heater air intake but could be modified for your use. Of course they would only be effective whilst moving forward or facing into a very strong wind.
Why not give them a go? They are relatively cheap and if they dont work you can put things back as they were and flog them on eBay.