tubular manifold

[warpspeed]

Alternatively, weld in anti-reversion cones......

 

[red reading]

Or don't run to much overlap and have a properly designed manifold

 

[warpspeed]

Bit difficult for me using the 16ve cams in the vvl head to get less overlap though, although when I have enough money I'll be speaking to cat cams about a custom pair of cams to suit the lpg

 

[Makaveli_se7en]

Ooooo ya clever git............who's going to ask what reversion is then?

:lol:

Bit difficult for me using the 16ve cams in the vvl head to get less overlap though, although when I have enough money I'll be speaking to cat cams about a custom pair of cams to suit the lpg

Adjustable cam sprockets would be the cheap option. But the other option is run longer headers to help counter the issue, however it doesn't stop the issue of turbo chill from running lots of over lap.

 

[pulsarmoley]

• REVERSION ​

Reversion is simply the exhaust gases momentarily flowing backwards during the overlap phase of the camshaft at low cycling rates. During the overlap phase the engine is on the exhaust stroke and the piston is pushing out the last of the exhaust gases. Prior to reaching top dead center the intake valve begins to open. At low cycling rates the intake charge and the exiting exhaust pulse have yet created any momentum. Thus the piston pushes some spent exhaust gas into the intake manifold. This is why engines with big camshafts idle and sound radical. The exhaust pulses shoot up into intake manifold causing a major disturbance. The cylinders receive an uneven mixture of air, fuel and spent exhaust gas. The piston then reaches top dead center and begins the intake stroke. At this point both valves are open, in fact the exhaust valve in some cases may not shut for another 50 degrees of crank rotation. During this 50 degrees of crank rotation the piston literally draws from both the intake and exhaust valves causing the exhaust gases will momentarily reverse. At high cycling rates the inertia of the incoming intake charge and the out going exhaust pulse keep the gases flowing in the proper direction. Not a problem until you add water into the exhaust stream. Concerning headers, reversion can be severe enough to add water to oil (milky oil), rust valve seats, even stall the engine. This effect only happens at idle, but engines encounter their greatest reversion pulse at shut down.
For this reason Lightning Performance Marine has developed guide lines to help you decide what options to add when considering an exhaust system.
Our guide lines are based on a 454 C.I. engine with a standard Mercury header and 8" long collector. The camshaft should be no larger than 240 deg. duration @ .050 lift. Lobe separation angle 112 degrees. Valve lift is not that much of a factor. These figures are just guide lines. Cubic inch displacement, valve size, connecting rod length, valve timing, etc. all have an effect on reversion.
THE ONLY TRUE TEST FOR REVERSION IS TO IDLE THE ENGINE WITH THE HEADERS ATTACHED AND WATER GOING THROUGH THEM, SHUT IT DOWN, REMOVE THE HEADERS AND IF YOU HAVE WATER RESIDUE LAYING IN THE EXHAUST PORTS, YOU HAVE REVERSION.
Lightning Performance Marine makes many options to reduce or totally eliminate reversion.

• ANTI REVERSION TIPS

1. Header selection The tip to header selection is to choose a design that will introduce water into the exhaust stream as late as possible. For example our 40340 header is actually made to replace a Mercury manifold with a 3" riser block. This header is 4" taller than a standard Mercury header plus it rocks forward 2" thus were able to add a 2" longer collector. If the height is not a concern you just added 6" of dry length to the header.
2. Collector selection If you have room to add dry collector length do it. Collectors are available in a variety of lengths.
3. Cubic inch displacement The tip here is simple, the bigger they are the harder they suck back. Either reduce the duration of the cam or start add some anti reversion options.
4. Camshaft selection With regards to headers the only thing your concerned about is how much piston movement in volume takes place while the exhaust valve is open on the intake stroke. A wide lobe separation angle actually advances the exhaust valve timing event which will close the exhaust valve sooner, but the down side is it also moves the horsepower and torque curve up the RPM range. Rhoades style bleed down lifters will deduce the cam duration by as much as 20 degrees. Available only in standard hydraulic these lifters are a great choice.
5. Connecting rods Marine engine builders rarely think of connecting rod ratios effecting reversion, but it does. A longer than stock connecting rod will make the piston dwell at the top during the overlap cycle thus less piston movement with regards to crank rotation.

Well this was an interesting read

 

[warpspeed]

:lol:



Adjustable cam sprockets would be the cheap option. But the other option is run longer headers to help counter the issue, however it doesn't stop the issue of turbo chill from running lots of over lap.

I have adjustable sprockets but I'm not sure how much running liquid injection lpg will affect things, running vapour injection lpg on a 1.4 c1j renault engine I converted I found a gt2560r was producing full boost a good 1800rpm earlier than expected even with a .83 instead of .60 exhaust housing, the standard log manifold but a piper 285 cam.

 

[RO_SUNNY]

If anti-lag will be used on an manifold made by me....than it will be made from another type of stainless steel and bot from the regular 304.
For an manifold on which anti-lag will be used i will make it from 310 stainless which will withstand a minimum of 1050 Cdeg. All my manifolds are back purged 100% and penetration is 100% as I bevel all my welds and also keep an corect gap (not like all the guys that sell 1500$ manifolds and say that they are with lifetime waranty).
I will use only 1 example (I have alot but this came to my mind now), the manifold which I made, for the evo9, is actually a copy of an Extreme Turbo Systems manifold which was cracked / rewelded 8 times and the guy which bought it from the USA pay'd for it almost 1400$. After that he came to me, I made the manifold and from then to now (almost 1 year) he had no issues with it.
Anyway....a waranty is a waranty and I will take responsabilty for each and every work that i will do and take money for it.

As a small thing, I am an naval architect and an welding engineer.....so I have used softwares for designing high pressure/high temperature piping systems alot until now.
Also I have inspected/made plan approval jobs/make welding procedures for high pressure/high temperature CuNiFe piping systems which are used onboard alot of ships and alot drilling wells/platforms.
Also I have we have been (the company where I am working) on the case study of the Deep Water Horizon (The Gulf Eco disaster of BP) of the piping system failure.

That being said I think i know a thing or two about piping systems....


Regards chaps,

Bogdan

 

[warpspeed]

A 'piping system' on a ship/rig is not a tubular manifold, knowing how to design/make one does not automatically qualify you to design/make the other.....
You would do well to listen to Makaveli

 

[Makaveli_se7en]

If you read my post I didn't question your abilities as a fabricator or the durability of the manifolds, although if it was my choice I would spec a nickel based super alloy for anti-lag applications as EGT can hit 1200C.

As per Warpseed's post; exhaust manifold flow is very different to pipe flow. Pipe flow has a very high L/D ratio and therefore can be effectively modelled using much simpler methods as the flow can be considered to be steady state with fully developed boundary layers and most of the time can be considered to be imcompressible. Before my current job I used to do some lecturing at a local university and one of the classes in the 2nd fluid mechanics course I taught was pipe flow. Oil and gas lines have some slightly different issues in that the flow is often multi-phase, something I know a little about as my PhD supervisor came up with some of the 2 layer and 3 layer modelling techniques which are now pretty much industry standard)

Exhaust manifold flow is very different, it is single phase, compressible and highly pulsating and requires a completely different set of analysis techniques.

 

[chopper]

99% of modders just buy something because its shiny or because others use it not because they have asked to see the flow charts and choose from there. I'm sure these are all valid points but you wont be able to tell the difference in your cars.
It has been said before that the standard mani is good till 400bhp but people running less inc me would like a ss mani just because they do. If someone wants to make one with a warranty or one that doeant break i'm sure people buy it as there is not much choice out there for a stong one which wont crack.
Everything that has beeen said i'm sure is a good point but we are not running F1 cars period.

Just my 2p's

 

[PobodY]

I think this is all constructive advice, and surely somebody has to ask about flow charts etc so that the 99% can have faith in buying something because others use it.

Nobody is suggesting Bogdan is making rubbish, but this is the difference between "great" and "superb".

 

[j0ff]

It's all really good reading TBH, i'm quite enjoying the fact that this thread hasn't turned into a slanging match (yet?!). There're some really rather clever people and some very skilled fabricators on here

 

[warpspeed]

99% of modders just buy something because its shiny or because others use it not because they have asked to see the flow charts and choose from there. I'm sure these are all valid points but you wont be able to tell the difference in your cars.
It has been said before that the standard mani is good till 400bhp but people running less inc me would like a ss mani just because they do. If someone wants to make one with a warranty or one that doeant break i'm sure people buy it as there is not much choice out there for a stong one which wont crack.
Everything that has beeen said i'm sure is a good point but we are not running F1 cars period.

Just my 2p's

You would be as well buying an ebay manifold and getting it braced then.....

 

[warpspeed]

I think this is all constructive advice, and surely somebody has to ask about flow charts etc so that the 99% can have faith in buying something because others use it.

Nobody is suggesting Bogdan is making rubbish, but this is the difference between "great" and "superb".

Exactly, get the design right in the first place and everyone will be happy to buy one, yes it's a bit more thinking and research involved but an old saying comes to mind 'measure twice, cut once'

 

[pulsarboby]

99% of modders just buy something because its shiny or because others use it not because they have asked to see the flow charts and choose from there. I'm sure these are all valid points but you wont be able to tell the difference in your cars.
It has been said before that the standard mani is good till 400bhp but people running less inc me would like a ss mani just because they do. If someone wants to make one with a warranty or one that doeant break i'm sure people buy it as there is not much choice out there for a stong one which wont crack.
Everything that has beeen said i'm sure is a good point but we are not running F1 cars period.

Just my 2p's

totally agree with that!

these are 20 odd year old bricks on wheels, if you can make something thats better than stock that doesnt warp or crack then your on to a winner i reckon.
you could count on one hand people that want to run antilag etc and at the end of the day at some stage their cars will be stripped and sold as spares whether it be 3 months or 3 years lol
the majority would just be happy with something thats a slight improvement over stock, doesnt break and looks better

thats my 5p worth lol


ebay manifolds arent worth bracing as the face plates often distort and buckle before they crack

 

[vpulsar]

Just my 2p's

You know what its about time someone with some common sense posted these brain boxes should try and get a life me thinks.



Rob

 

[j0ff]

here we go...

 

[warpspeed]

Lol, he's just bitter, he does own a bmw mini and a saab after all....

 

[vpulsar]

Lol, he's just bitter, he does own a bmw mini and a saab after all....

No Mini anymore I'm afraid though I do miss the super charger whine, I have a 1990 Saab T16S Aero and a 3.0lt diesel A4 Quattro avant now so nothing to be bitter about lol. As the guy says who gives a flying monkeys toss if it flows enough for 400 bhp or 403 bhp because that's about all you're talking about with this flow bollox.

Which maybe of importance to a professional drag racer looking for the odd 10th here and there but to the average forum member looking for a bit of bling to brag about down the pub with maybe a little better performance as a bonus I doubt it matters at all, What they want is something shiny that fits well and doesn't crack every 5 minutes.




Rob

 

[shroom]

"Makaveli_se7en it is single phase, compressible and highly pulsating and requires a completely different set of analysis techniques."

Like a big dildo then? maybe the best way to analyse it is to stick it up your ass