Intake manifolds - diesel vs petrol

[nastytroll]

at cruise the boost level and temps are low. the thing with diesel engines is they don't limit air flow to control engine speed. So this tuning can be used to improve efficiency at cruise. It doesn't always have to be about peak power.

At cruise my 4wd runs about 9psi. Give it a headwind and it's 12psi.

Have a play with this calculator and see the difference it makes:
http://www.sengpielaudio.com/calculator-speedsound.htm

At cruise (100km/h), our td42's run between 2-5psi. 1 ute and 1 wagon.

Interesting read.

[-Scott-]

Have a play with this calculator and see the difference it makes:
http://www.sengpielaudio.com/calculator-speedsound.htm

So, as boost pressure rises so does temperature, so the pressure waves travel faster, so the sweet spot will move up the rev range.

Obviously, as boost rises you'll need to drive faster to maintain engine efficiency.

"Honest, officer! I had to drive faster to improve my efficiency."

[brad-chevlux]

Obviously the resonance frequency matters (see 2 stroke petrol) BUT

I was thinkign of simple differential flow, and EGT's variance.

What in a petrol would lose you some power, in a diesel could kill the motor.

I would like to know which is more significant, flow restrictions, or resonance patterns.
I suspect the resonance would be the same boosted or not, but the points and benefits would change.
Boosted doubles the pressure diff between cylinder and manifold, so 10% from resonance is less critical (to my thinking)
Then again - 10% of doubled mass is still significant.

It would be interesting to measure EGT variance with OEM vs custom "adhoc" manifolds.
I know the 1HZ manifold has some "tricks" up it's sleeve for what looks to be a very small, simple log design.

Paul

anyone with an EGT gauge could help here, multiple probes in the exhaust manifold through a switch to select witch probe is being displayed on the gauge.
You would want to see reading from either the front 3 or back 3 cylinders.

Boosted engine where full throttle power is the concern out right flow and even flow would be the most important part.
Ford went down this path with it turbo 6cyl engine. The manifold looks the same from the outside but is not fitted with any of the runner switching hardware.
But with petrol engines air flow is limited to control engine speed, so any gain from runner tuning is pointless at cruise.

Diesel engines are different. they don't limit airflow at all (most not all diesel engines anyway). so runner/plenum tuning takes on a whole new role. Even if your engine makes boost at cruise speeds you could still benefit from a tuned intake. If you can get more air into the cylinder by good intake design the engine doesn't have to work as hard.


Obviously there is a lot to consider and it not something you can just knock up in a day and have it work. But thats not to say there is no benifit.

What in a petrol would lose you some power, in a diesel could kill the motor.

Can and does kill petrol engines too. port injected EFI will still go lean on the cyls getting more air.

[KiwiBacon]

Even with huge changes in temp a well designed manifold on a TD42 or 1HZ will out perform the compromise that is the stock item.

Well time for you to make a prototype and test it.
It'll be very easy to do, simply run the engine at a fixed speed (say 2000rpm) and measure air consumption. Do it again with the new manifold. A higher air consumption reading will mean you've acheived better VE.
You'll need a dyno cell test to prove better fuel economy and improvement under boost though.

However, I doubt you're going to make any meaningful improvement. Feel free to prove me wrong.
Much like the people who criticise the exhaust manifold design on modern diesels. The diesels which trump everything else for both power and economy.

Here are some inlet manifolds from the most efficient diesels on the road. VW TDi's.

130/150 hp version


90/110 hp version


2.0 tdi.

[brad-chevlux]

Whats the point. We might aswell lockt he thread now. Kiwibacon is god.
VW has made it quite obvious that he stock TD42 and 1HZ manifolds are the perfect design for every application.

[GreyPower]

This is a standard Toyota 1KZTE manifold. A shocker.

This is after many hours of cutting & fabrication. I can't tell the torque gain ecause I changed the intercooler at the same time, but throttle response & driveablity are definitely crisper

[KiwiBacon]

Whats the point. We might aswell lockt he thread now. Kiwibacon is god.
VW has made it quite obvious that he stock TD42 and 1HZ manifolds are the perfect design for every application.

Sorry, I thought you were looking for robust discussion based on proven concepts.
My mistake.

[brad-chevlux]

I was, but what did you think was going to happen when you start posting pictures of completely unrelated engines and then tell me i need to go and spend a few thousand dollars on dyno time.

you were looking to end the discussion, so i ended it.

[KiwiBacon]

I was, but what did you think was going to happen when you start posting pictures of completely unrelated engines and then tell me i need to go and spend a few thousand dollars on dyno time.

you were looking to end the discussion, so i ended it.

At what point do different turbo diesels stop being related?
You'll notice that all the designs boil down to a plenum and runners. There's probably a minimum plenum size in relation to cylinder volume but otherwise they're all following the same rules.

Here's a BMW 6 cyl diesel which pokes out over 200kw. They run 42psi boost. Probably just another unrelated diesel. Same thing, a plenum and runner manifold, this one fed from the front end.


I actually told you to build a prototype, the dyno testing comes later, the first few tests will be quite cheap and only require an air flow meter.

[brad-chevlux]

again posting usless photos to try 'prove' that there is no gain to be had in a well designed manifold. what you fail to see for some reason is that all of photos prove there is a gain to be had. compare them to a TD42 manifold
do you see it yet?

or must it be pointed out. for a start look at the plenum size and volume compared the size of the engine it feeds,

This discussion was about more then just runner length, you seems to focus on side of though.

you give me the money, i'll build a TD42 intake manifold that make more power.

i look forward to your next photo of a late model high performance diesel.

[KiwiBacon]

again posting usless photos to try 'prove' that there is no gain to be had in a well designed manifold. what you fail to see for some reason is that all of photos prove there is a gain to be had. compare them to a TD42 manifold
do you see it yet?

or must it be pointed out. for a start look at the plenum size and volume compared the size of the engine it feeds,

This discussion was about more then just runner length, you seems to focus on side of though.

you give me the money, i'll build a TD42 intake manifold that make more power.

i look forward to your next photo of a late model high performance diesel.

Mutterings about irrelevance aside, what modifications do you plan to make and what gains do you expect to see?
Now you're back to talking about non turbo engines, does this statement no longer hold?

You might find a gain if you spend alot of time designing and building manifolds, but unless you find the challenge enjoyable, it probably wouldn't be worth the effort.

I'm impressed that you can calculate volumes visually. The biggest problem I see with the likes of the TD42 manifold is the air entry.

[brad-chevlux]

the problem started when i said made a general statement that a better manifold would benefit a TD42 or 1HZ,

You for some reason took that as me saying there are huge gains if you jam in long runners.
then started on some rambling of your own finishing off with telling me to go and spend money to prove you wrong.


IF you wanted a real discussion you would have gone about this a different way. You obviously aren't willing to add anything to the thread or you would have made useful posts, instead you post pictures that now by your own admission can prove nothing just by looking at the outside of them.
I ask why post them in the first place?

Until you are willing to have a real technical discussion and stop with the ego padding i'm not going to discus it anymore.