hexxon

Post it in, right away!

CozzyBrom

it dont at the min thow

rear end all droped out way
no gear box tunnel all modded for new gearbox
and engine bay is just bare bit of wiring thats it lol

hexxon

Cool pieces... But not my cup of tchae... A lot of horsies there right? A lot at the top end, not so much in average?

Stu @ M Developments

iTrader: (12)

Ok.. its carefully written in laymans terms and is taken from this topic about Surge: https://passionford.com/forum/viewtopic.php?t=34511
--------------------------------------

Ok,
Im feelin a bit low tonight and need summat to pass the time away, so maybe a small essay will help?

Brief explanation:
Surge is caused by stall, which is worsened by surge, its a vicious circle...

Imagine the way our turbocharger's compressor is driven, right back to basics: The turbine wheel is spun by exhaust gas, utilising also the energy stored in the exhaust gas as latent heat.

This force on the turbine shaft generates torque at the compressor end as they are physically connected. Remember that part as its the key element, Torque

Ok,
Now lets imagine our turbocharger compressing air, forcing it into the engine, the engine is utilising it.. what happens then? Ok, The engine expells it, and our turbine housing pressure goes up accordingly, the torque applied at the turbine wheel increases, increasing the spin speed and compressor efficiency at the other end. Great chain of events!
End Result? boost is climbing nicely.

Ok,
Now imagine this scenario:
The turbo begins to spin, as above, but the compressor wheel is generating more air than we can move and the torque required to spin that huge compressor is not being met? Remember that unless the air is processed by the engine, and expelled as hot, rapidly moving air into the turbine housing, our turbine shaft torque will not increase to spin the compressor faster, and it may well diminish.. our compressor is slowing, braked massively by the compressed air its trying to overcome and increase.....

Result? Compressor starts to slow a little.. (beginings of a compressor stall)

Ok,
So now what?
The engine is still rotating and consuming air, but the turbo has stopped producing an excess, so our engine has now had chance to consume what excess was available and the inlet pressure is now diminishing, the turbine torque is now increasing again...

VERY IMPORTANT:
Remember also that at same time, compressor resistance to spin has also dropped due to housing no longer being as pressurised and as a result, the torque required to spin it has dropped massively..

Boom.. Suddenly the Turbine wheels torque massively exceeds the compressors resistance and the turbo spins to speed in an instant!! Sounds great, rapid boost climb!! The compressors acceerating at over 2G

BUT:
We just hit the same problem again, our huge compressor has made so much boost, so fast, and is trying so hard to push the massive volume or air, that our YB cant use it.... so we start to slow again........

So we went: Fast, slow, fast, slow, or in other words: The turbo is Surging.
As you can imagine, it continues this cycle until it hits the revs your engine consumes all the air.. then your away!!

Downsides to this surge are pretty obvious:
We can have serious bearing wear, due to the excessive loads imparted on the shaft supports.

Compressors have been known to simply explode!!

Worst case scenario, the compressor being slowed rapidly with a turbine still trying to accelerate it can simply do as expected, part company.

Hope this helps to explain in as simple terms as i can put it, the phenomena known as "Turbo Surge."


Hope it helps and doesnt cause a huge argument like it did on teh other post

Stu @ M Developments

iTrader: (12)

Someone resave and resize those pics for me and il delete the originals and relink em in the correct places as this is a great topic and its now too wide

CozzyBrom

all these big power cozzys fook the thermostat housing off and run out the head and water pump but where the the water feed out back of head go to ?
normally it goes back into the thermostat housing on a 4x4 and a water pump on 2wd but i see from the pics thats a 4x4 pump
what gains are they of doin it like this

Jallu

Yes it's pretty common to move the bulkhead backwards few inches (and engine too) so the cooler and radiator have some space as well.

Here's my friend mk2 with 520bhp and the plenum is orig cossi. Turbo is rs500 spec to4

hexxon

Having a hard time agreeing with you here... Theres quite a few advantages with running internal wastegates, which are working correctly, one of them is a heck of a difference in turbo-response. Thats no small factor that...

Stu @ M Developments

iTrader: (12)

Right.. ive fixed all the pics for you all. Just keep em to 640x480 or below now please fellas. Photobucket users click on "edit" to change pic size

CozzyBrom

mmmmmmmm i rember that post
the old argument of t4 boost v t3 boost and the volume of air consumed
your a clever little c.unt arent you

Stu @ M Developments

iTrader: (12)

That was a different essay Brom.. that was a REALLY big one and took me around 5hrs to write.. ive got that here too...

And less of teh little..

Stavros

I didnt say External Wastegate anywhere on there was better did i? Doug did I didnt mean that at all...

What i was saying is Garrett only made the GT30 (well its GT30R really) as external wastegate, and the internal wastegate versions available from some hubrid turbo makers are not the same, they a turbo cobbled together from GT30 and old T4 parts...

They might work OK, but they far from ideal...

hexxon

Great stuff Stu, well written mate. Theres no need of arguing on that one. Starting to become a nice thread covering flow in turbocharged engines this one, dont considering exhaust and the most important of all, the cylinder head. Perhaps this will come to interest later on...

Porkie

iTrader: (1)

May I just add well done Jano , for starting a great topic and getting some awesome input from some new and interesting people

CozzyBrom

post it post it am sure our newbies from over the sea will like a read of it

and as for the little well
am the big c,unt and u next to me wud be like danny devito and arny in twins

so what would you like to be called oh great one

Stu @ M Developments

iTrader: (12)

Many thanks Patrick.
Maybe this topic could take and benefit from my turbo size essay that explains in similar laymans terms (Hard terms to come up with ) how a T4 gives more horsepower than a T3 at exactly the same boost pressure. Something i found difficult to explain to customers at teh best of times... but succeeded with this topic i feel

If anyone thinks it will be of interest il dig it out.. im leaving for home now.

Stu @ M Developments

iTrader: (12)

May i just add to newbies that I am 5'11" and 15stone.. Brom is just erm... bigger than that.

hexxon

My, tad special, GT30/35 hasnt got any t-series-pieces in it. And it is internally wastegated But lets not go into that.

CozzyBrom

true a very good read and nice to have input and replys
lets talk about manifold design aswell
4 into 1 4 2 1 and primary lenghts bore sizes best wastegate pos and size
cool post

hexxon

Of course, post it and perhaps we could evolve it into understandable then

Stavros

That sounds like a good turbo Youd sell shitloads of them over here...

CozzyBrom

dont lie stu tell the truth your 5.1

i am 6.1 and 21 st
the big poper bear of the cozzy world

hexxon

Well start up then papa bear! What is the interesting criterias for a manifold according to you?

hexxon

Ok, well, its a nice piece, though somewhat limited in power output for some of the guys here...

CozzyBrom

like i said earlyer all i do is weld things together and do one off fabricatoin
engine dynamics are beond me
but am happy to learn and take new things in
i would say the main thing for a mainifold is not to crack
now the way i see it is
crackin is caused by metal expanding contracting therefore bending under heat due to the shape of a cozzy manifold the angle at which the ports come out the head makes it very hard to design a manifold which wont crack
a C shaped or curved manifold tends to open out so to speek then hot due to expactoin over a curved pipe ?????
so the only way i see a manifold not crackin is using some kind of slip joint like on a rs200 so it gives the manifold some way of expanding contracting
as for primary lenths thats all beond me mate

also my typing and spelling oh here aint to good either so what i just posted may be imposable to understand

Stu @ M Developments

iTrader: (12)

Ok,
Best grab a beer before you start this one
This topic was taken from a discussion a long long time ago and folk were arguing about how a turbo at 21psi could flow any differently to a larger one at the same pressure... my reply was this:

------------------------------------------------------------------

Let’s go back right the way to basics…

Why is it, that a turbocharger is universally is recognised as the ONLY form of forced induction that COSTS power?

Well let’s look at this shall we?
We have a decently specced engine, say an Rs2000 I4 and we are making 170bhp through our otherwise std setup with some head mods and cams.

To make this power we are utilising the air pumping ability of our 4 x 500cc cylinders.

They are drawing in enough air and fuel at the correct ratio and importantly, expelling it again to produce this power. This ability incidentally is related to its volumetric efficiency which i will touch briefly later.

The I4 is making its 170bhp with its nice, well-designed STANDARD 4-2-1 exhaust system.

Let’s now redesign it in the great Ford RsBB fashion and remove the nice exhaust system and stick a tiny pathetic straw sized .48A/R turbine housing on it with a closed wastegate and the turbocharger actually welded tight so it can’t spin.

Does ANYONE on this BB think this engine will now make 170bhp? Well It will be very lucky to make 120bhp now.

So whats happened?

WE HAVE INCREASED PUMPING LOSSES DRAMATICALLY.
This is the biggest issue. The reason this costs us power, is a great proportion of the energy produced from the power stroke of 1 cylinder burning our nicely presented charge of fuel and air is now wasted trying to push the spent gas out of the previously active cylinders exhaust valve and through the tiny turbine housing.

We now have some detrimental knock on effects:
The friction on components caused by this pumping loss now adds heat to our engine too. This heat was part of our power strokes energy.

This pumping loss has also caused the overlap events effective scavenge volume to drop massively as the nice, meticulously calculated pulsation vacuum that designers spent hundreds of hours to create has now been exchanged for BACKPRESSURE.

This backpressure has now also decreased the amount of air the exhaust pulse drew through the inlet valve at overlap when piston speed was at its lowest so maximum cylinder fill has reduced, down goes VE.. Things are looking bad for our power curve now.


So conversely, as we now have LESS airflow on overlap, we are going to start dumping heat through our exhaust seat and port and are heating our soft alloy head up.

WHY? Very simple ,
Designers use scavenging on overlap as a very simple and very effective way of cooling valve seats, guides and ports.

How? Also very simple ,
As we reach overlap in our cam timing event we have both COLD inlet and HOT exhaust valve open, this gives the exhaust valve and relative components time to be cooling from their grievous job only moments ago of shifting a mass of immensely hot air through its system so it’s a great relief to sit in some nice cold flowing air for a second and transfer a bit of excess heat away!!

Our fancy new engine / design isn’t looking too hot now is it? (Well actually, its getting damn hot.. )

So,
I hope this large and simply worded explanation helps you to understand that a turbo DEFINATELY costs power by its very presence on your engine and also why it does so?

Ok? Good!!

So what the hells that got to do with today’s BB argument? Oh yeah, sorry........

Exhaust backpressure caused by the turbine housing assembly’s restriction is our key element between T3 and T4.

But let’s deal with the delivery of our air first and we will use the good old YB for our examples.

A T4 produces far more VOLUME of air at a given pressure from its HOUSING than a T3.THATS UNIVERSALLY AGREED.

Now if we quickly use this bizarre volume of air example supplied by someone earlier...


quote:
--------------------------------------------------------------------------------
Foolishly, sorry, Originally Posted by erm.. someone
Look at it this (simple way so you understand ), imagine a 1 ft diameter balloon inflated to 15psi. Then imagine a 2ft ballon inflated to 15psi - are you trying to tell me that both have the sane volume of air in them?
--------------------------------------------------------------------------------



That balloon is actually bigger so yes it holds more volume, but this is not applicable to an engine because even if we take all the inlet valves out and pressurise the system with our turbochargers, we are still presenting each turbocharger with the same volume to fill, lets say 2000cc for the cylinders and 1000cc for the intake of the head and the plenum / hoses.

So we have a 3000cc volume to pressurise with air. This does not change unless the engine begins to operate. An engine will only generate more power by shifting more air at the correct AFR. SIMPLE.

The engine will only shift more air if we do one of the following:

1) Improve the airs route into the head.
2) Increases the pressure we push it in with.
3) Improve the mapping.
4) Improve the volumetric efficiency.

So,
We still know a T4 WILL make more power than a T3 at the same boost so why is that?

We don’t appear to have done any of the above mods do we?
The head hasn’t been ported.
We are running the same boost.
We aint touched the chip cos PHIL cant remember what spec it was for!
So have we changed the engines VE?

Good question, and back to turbo’s.
A T3 50trim with our desired pressure ratio of 2.4 (14.7psi inlet +20psi outlet divided by 14.7psi inlet) will be spinning at 134,000 rpm with a compressor efficiency of 70%.

A T4 60 trim with our desired pressure ratio of 2.4 (14.7psi inlet +20psi outlet divided by 14.7psi inlet) will be spinning at only 97,000 rpm with a compressor efficiency of 82%.

Now lets go to the turbine housing.
The T4 P trim wheel flows a lot more air than the Std T3 trim rear wheel. (They are all the same as std on T3) but it conversely takes more to spin it to speed.

We now have an exhaust backpressure IMPROVEMENT due to a better flowing rear wheel!!!!!!!

Secondly,
We now have a wastegate that will open much sooner and much wider than it would on the T3 as less exhaust volume is required to spin the turbine as we have a 37,000 rpm improvement in efficiency at our 20psi.

HEY, we have another exhaust backpressure IMPROVEMENT.

If our T4 is using a bigger housing, and it IS if compared to a T3 we have another exhaust backpressure IMPROVEMENT!!

So lets go to boost at the intake:
Now our exhaust backpressure is reduced, our cylinders demand for air has increased. We have overlap efficiency gains, we have thermal efficiency gains so we can suck more air and we can suck it with a greater pull because we are actually revving more freely so our peak piston velocity has increased.

So we are CONSUMING more air and this T4 can supply it for fun… But… we aren’t making more power because the T4 pumped more air at 20psi.

We are making more power because this turbo improved the volumetric efficiency of our engine mainly through exhaust backpressure reductions and an improvement in outlet temperatures at the compressor outlet due to Adiabatic Efficiency which we may or may not discuss later.

Goodnight folks,
If anyone wants to know what the compressor maps do and how to decipher the turbo specs, let me know when ive slept cos this essay took me four hours to write in a fashion that anyone can understand!! It would take about 15mins using techie terms

Best Regards and goodnight,
Stu

Its only had 600 odd views in technical essay forum Hardly worth my while writing it

CozzyBrom

ok stu we keep our pics small if you dont post no more than 100 words a post

am getting with drawal symptons am gona go make me some rear hubs and weld away

back soon

Mike Rainbird

iTrader: (3)

Stu,
Funny, you rediculed my baloon anaolgy in that discussion, but then someone used it recently and you concurred that it was a good analogy .

Stu @ M Developments

iTrader: (12)

Eh? I still think its damn stupid
Perhaps i was pissed...

BTW... i removed your name from that essay.. so have this for incriminating yourself

Mike Rainbird

iTrader: (3)

Brom,
The cracking is also down to the fact that the YB engine has some serious NVH issues at 4k. If properly designed and supported, then a tubular manifold will be okay.

hexxon

Ok. The matter of manifolds cracking is a lot due to heat fatigue in the material, some materials are more resistant to this than others. Creating a manifold in plain steel just isnt a smart idea for example, since it hardens easily -> the manifold cracks during time. Stainless steels like 2346 and a lot others is much more resistant to heat fatigueing. Another thing to properly think over when creating manifolds is the fact that supporting the loading on it in some way, dont let the turbo hang in the air... Use some kind of damper, its a nice solution. When using long curves, c-shapes and u-shapes, a smart thing is to support the bends from the weight of the manifold using the manifold itself

I could easily understand what youve written, so theres no sense for you in saying that!

CozzyBrom

mike this is no dig and corect me if am wrong the exhuast manifold you sell are the same as the one rod has
no cortect me iff am wrong he publicy stated that it snaped off where the wastegate neck was and had to be braced aswell after
so its not just design
theres companys avertising inconel (spelling) manfiolds at over Ł1400 but when asked what its for (cozzy) sorry no warrenty and these ppl make f1 exhausts
karl has even spoke to cosworth about this and they state no way any tubulair manifold will work on a cozzy with out cracking again due to the shape of the port going out the head
the only way is to have one one off cast
my haywood and scott wrc manifold cracked every week and that was braced to the engine mount aswell
am only lookin for answers i am not having a dig mike

Kev.H

Brom sorry im dumb but do u mean every tubular manifold will crack

does it crack cos of heat or cos of weight of turbo and movement ??

Mike Rainbird

iTrader: (3)

Brom,
The one that Rod has was not designed correctly. Once they reverted to a correct design, the problem disappeared. However, I understand that Rod cured his particular problem with some Brom stylee industrial bracing .

There are 12 manifolds done to this design that have not cracked yet... .

Anonymous

Hi
my manifold cracked orginally on the Dyno, It had a very long Pipe venting out through the roof hanging off it. In hindsight this was crazy but no one thought about it.
The cracks were not noticed & put back in the car on start-up the prob was obvious. The manifold was then braced by Marks Fabricator & the details sent to Sweden. We have also modified the flange where the external wastegate fits & its now much less Bling but works.
The changes have been done at the manufacturers expense & he his greatfull for the feedback.
This manifold put looks before design & i was not happy about that, cant say that this the end of the matter but at the mo its working well with no probs & yes the car is being given grief cos everybody & his dog wants a ride,
Rod

HYBRiD_T

FANTASTIC READ!!!

Has anyone tested PJ's new manifold?

Stu @ M Developments

iTrader: (12)

Lets see how much it is read:

18:36pm and 3252 views.

hexxon

Stu, nice one that as well. But a bit light at points actually, concerning exhaust backpressure. So im going into it briefly

Exhaust backpressure is not always a negative thing. For starters at a certain rpm, for a certaing displacement, a certain pipe-size, or turbine housing-size, will get sudden increase of backpressure, which will increase dramatically from there. Right. Having exhausts flow easily is nice for the output, correct so far, but not for accelerating our precious turbine wheel! Before elaborating more deeply, i need to state, that EVERYTHING concerning flow in an engine is a matter of precise balance.

Balancing cross-sectional sizes for flow is one of those matters, for a certain inlet flow in a head, a certain exhaust flow will occur at a certain A/F-ratio and RPM. This is proportional. Different sizings of the pipes on same flow will increase or decrease the backpressure, as well as the gas velocity, on both intake and exhaust. Different sizings will therefore allow the air/exhaust to travel from one point to another in different time, this is the basics.

Now lets examine the case of backpressure in exhaust manifolds/turbine housings. There is a clear advantage, concerning spool-up, to have as fast exhausts as possible colliding with the turbine wheel. This is simple, as faster exhaus gases will increase the acceleration of the turbine better than slower ones. Having them being too fast for a certain engine at a certain rpm, is a case of making the turbine transfering so much torque to the compressor that the compressor will generate surge, as brilliantly explained before, or generating extreme amounts unlogical amounts of backpressure. Having the exhaust being slower than necessary, that is, the backpressure is way low(good?) and the surge is far out of hand, is a case of generating a slow spool-up.

Now, we may want to consider the options here. Backpressure is always present, in different amounts. Good spool-up will increase the lower rpm-range of power in case that the rest of the engine can swallow the air supplied. Bad spool-up will leave the engine unboosted, working as a NA engine more or less. How good is a NA engine with a CR of say 7.6, which seems popular? Either we increase the base CR or we think for it a while and increase the boost that the turbo is supplying for us at the interesting rpm-range.

What i want you to think about at this stage is the actual importance of not using too big housings and turbine-setups for the revs and displacements that you are running with. But what is equally important, size up the pipings in the manifold suitable for this as well, its dead important! Backpressure in this form can be lived with to quite some extent, its about balancing the pros of having boost/or not and the cons of the extra heat.

Heat, yes. Summer is nice dont you think? Winter is cold, and we get slow and stiff... Well i do get stiff on other occassions as well. But that doesnt have anything to do with flow... Err, well it actually has. Shite. Well cut it! Heat. Air at different temperatures takes up different amount of volume. The hotter the gases the more volume it takes up. Basic. The more volume it fills up in a certain time, the faster the gases need to flow to fill it up. Therefore, warmer gases makes spool-up faster. This means, a engine capable of taking warmer air, could be made to spool-up better.

Now, lets talk about backpressure more into deep. What is it actually? Backpressure gets generated when turbulence comes into play basically. Turbulence can be created because of gas speeds so high that the inner walls of the piping restricts its continuance due to friction, a case of small pipes. It can also occur because of rough/inapropriate surface. The first one can easily be eliminated, adding larger pipes if its considered necessary, based on the facts ive aldready mentioned. The second case though, is MUCH more interesting according to me. Here the real black art of exhaust flow comes into play, how does the exhausts want to move inside the pipe to get a nice transport from A to B? Do they want to encounter bumps once in a while, due to welding, bad fabrication or plain stupidity? Do they want to move through strange radiuses and twists? Do they suddenly want to encounter a sharp edge due to bad matching between two surfaces? The answer to these questions and many more... NO!

Turbulence in this way is our evil enemy. Eliminate him, and the princess is ours to divide and conquer... Err Backpressure however is not always bad, which i hope that you might understand a bit better now. This is atleast a basic of my view of it.

hexxon

LOL, "everybody and his dog".

Well, cracking manifolds is due to two different problematics basically. Torque onto material unsuitable for it or heat, making the material less resistant to torque on it. Both of these can be solved. Why not apply ceramic coating inside the manifold? Why not make proper supportings for the manifold, easening its burdens. Proper.

hexxon

Perhaps theres a slight interest after all

Is that reading a lot in here?