Controlling head lifting under boost.

[turbotoaster]

Hi guys,

I was wondering what your thoughts were on this.

Im trying to work out a solution for a potential problem i think will be coming up soon on an engine im developing.

Its a Rover K Series Turbo.

Now at the moment we have run it in anger at 25psi of boost pressure and make 470bhp and 370ftlbs.

The aim is to reach 550bhp and maintain a flat torque curve of 370ftlbs so keep cylinder pressures in check to avoid head lift and let the RPM bring the power.

Rev limiter is set at 8200rpm.

Now I understand head lifting can be caused by controlled cylinder pressure(torque) and uncontrolled(knock) but as we start to increase the boost to around 33psi, it might start becoming and issue.

The main problem with the K series is that it used 413mm long M9 stretch bolts to not only hold the head down but also apply clamping force to the lower girdle to keep the main bearing journals round.

The K series engine expands from cold to operating temperature and the stretch bolts maintain an even and consistent clamping force thoughout this.

But being simple stretch bolts they werent designed for what im trying to do.

The issue I see is by replacing them with an ARP stud and nut kit is you can potentially end up with the mains being pulled out of round either when hot or cold due to this expansion. This was infact confirmed by TurboTechnics when they included them in the 260bhp supercharger exige engines and had excessive main bearing wear.

With that being the case, apart from obviously control the amount of torque the engine sees, would anyone have any other ideas that maybe I havent thought of.

[DVandrews]

I’ve put together a couple of engines using a steel oil rail and ARP studs, to cope with the extra clamp the main bearings were re-honed under maximum clamping force , a little was faced from the block and ladder prior to the machining, the other problem with extra clamp load is collapse of the pillars surround the bolts in the head when clamp is increased..

Dave

[turbotoaster]

DVandrews said:

I’ve put together a couple of engines using a steel oil rail and ARP studs, to cope with the extra clamp the main bearings were re-honed under maximum clamping force , a little was faced from the block and ladder prior to the machining, the other problem with extra clamp load is collapse of the pillars surround the bolts in the head when clamp is increased..

Dave

the engine seems ok running at 370ftlbs and doesnt seem to give the impression of pressurising the coolant up to yet, now while im happy to maintain that level of torque, we still dont know where the limit is on these engines, so i can simply just keep increasing the boost but im guessing the head lift has to be the next issue I will come across as i dont think I will have any component failure in the bottom end as im not using silly RPM and the other major components are aftermarket.

The pillar collapse, is this something your expecting or has actually happened?

[GreenV8S]

I assume your concern is the increase in chamber pressures from the extra boost. However, given that you aren't planning to increase peak torque, are the peak chamber pressures actually going to increase significantly? As far as I can see, you're aiming for the same pressure just at higher revs. The head gasket doesn't care what the revs are.

[turbotoaster]

GreenV8S said:

I assume your concern is the increase in chamber pressures from the extra boost. However, given that you aren't planning to increase peak torque, are the peak chamber pressures actually going to increase significantly? As far as I can see, you're aiming for the same pressure just at higher revs. The head gasket doesn't care what the revs are.

not really from the extra boost at higher rpm to force feed the engine to ensure the torque doesnt drop off.

I guess its more that i am leaving torque on the table, the engine might take 450ftlbs, it might lift the head, but if we get to that stage the thoughts were whats the best course of action if I decide I want that much torque(the car only weighs 700kg)

My concern was the stud kit wasnt the line honing after the block had been put in an oven, it was how the mains would be when the engine is cold as everything will contract, will they still be round for example

[Ive]

in the Honda K-series world, folks build the engines with bigger main bearing clearances for high HP or track work.
I have build mine with 40-45µm vs the 20-25µm Honda uses.
You compensate with a higher weight oil.
That might be a work around.

To what bearing clearances have you assembled the forged engine?
Codes are only a first starting point as aluminium engine blocks "work" as they age though heat cycles.

Forces from rotational components by far exceed forces from cylinder pressure at high rpm.
I'd shy away from the 8000+ rpm range with a OEM crank independent of the actual boost level.
Once you are knock limited, peak pressures won't increase anymore at higher boost levels, the forces will just act for a long duration over the work stroke.

Just drive it a season with 450HP and get an idea of how the package performs before going any further.

if you quickly want to find out where it lifts, just increase boost until it blows the coolant. :-)

[turbotoaster]

Ive said:

in the Honda K-series world, folks build the engines with bigger main bearing clearances for high HP or track work.
I have build mine with 40-45µm vs the 20-25µm Honda uses.
You compensate with a higher weight oil.
That might be a work around.

To what bearing clearances have you assembled the forged engine?
Codes are only a first starting point as aluminium engine blocks "work" as they age though heat cycles.

Forces from rotational components by far exceed forces from cylinder pressure at high rpm.
I'd shy away from the 8000+ rpm range with a OEM crank independent of the actual boost level.
Once you are knock limited, peak pressures won't increase anymore at higher boost levels, the forces will just act for a long duration over the work stroke.

Just drive it a season with 450HP and get an idea of how the package performs before going any further.

if you quickly want to find out where it lifts, just increase boost until it blows the coolant. :-)

due to the oil that i use 15w50 and the higher rpm and torque the engine sees I went to the limit of the recommended clearances on the mains/big ends of 0.05mm, so i have no concerns really about the bottom end in terms of strength as the compenents should be fine for my low 4 cylinder power output, running it at 360ftlbs at 8000rpm gives me the 550bhp im looking for, so I dont really want to run it to 8500rpm if i can avoid it, saying that i know someone who runs his to 8700rpm in a mgzr running alot of judd parts making 250bhl/180ftlbs.

The engine has hit MBT at every point in the rev range while hearing no knock at all, so I dont think we will need to worry about that, especially being 7.7:1 compression.

The turbo is good for 40psi, so as you say, you wont really know until we finally pressurise the coolant, im going to put a little pressure sensor in the coolant pipe when we are back on the dyno to keep an eye on it

[DVandrews]

You can use conical washers on the bolt holes to help adjust the clamp between hot and cold...

Dave

[stevieturbo]

turbotoaster said:

With that being the case, apart from obviously control the amount of torque the engine sees, would anyone have any other ideas that maybe I havent thought of.

Not using a K-Series ? lol

If you're restricted with head fasteners then you're fighting a losing battle. Unless someone out there has a head gasket, o-ring, or whatever solution that might allow it to work with a low clamp solution.

But most o-ring type setups seem very hit or miss to get right.

From what I've heard the strongest are a design with a triangular shape ring, it requires no grooves etc but does require a correct thickness composite gasket to seal waterways etc. The ring essentially just bites into the cylinder head, and the flat side against the top deck. Whilst this works very well, it does eat the cylinder eat each time it is bolted together.

[Boosted LS1]

Sodium filled Wills rings will help. The ring section is oval when clamped but if the head lifts they expand. It's a lot of work to fit them though. I've used them on a v6 cosworth and a 12v.

[turbotoaster]

stevieturbo said:

Not using a K-Series ? lol

If you're restricted with head fasteners then you're fighting a losing battle. Unless someone out there has a head gasket, o-ring, or whatever solution that might allow it to work with a low clamp solution.

But most o-ring type setups seem very hit or miss to get right.

From what I've heard the strongest are a design with a triangular shape ring, it requires no grooves etc but does require a correct thickness composite gasket to seal waterways etc. The ring essentially just bites into the cylinder head, and the flat side against the top deck. Whilst this works very well, it does eat the cylinder eat each time it is bolted together.

The triangular shape is a cool idea but as you say, i cant afford to replace a ported heavy everytime it needs to come apart.

I guess the payen MLS gasket i use and running the liners prouder than factory will have to do.

I do like the K series for its lightweight compared to alot of other engines, its not the strongest but i think at around 80kg its a good choice for a 700kg car, pretty much anything lighter is a bike engine i believe.

The reason i wanted to start pushing it as i think the car could be pretty good over a quarter mile, its already ran 11.4 at 131mph on 19psi on low profile road rubber so im hoping with the drag tyres ive ordered and 30psi+ we could get mid 10s

[stevieturbo]

turbotoaster said:

The triangular shape is a cool idea but as you say, i cant afford to replace a ported heavy everytime it needs to come apart.

I guess the payen MLS gasket i use and running the liners prouder than factory will have to do.

I do like the K series for its lightweight compared to alot of other engines, its not the strongest but i think at around 80kg its a good choice for a 700kg car, pretty much anything lighter is a bike engine i believe.

The reason i wanted to start pushing it as i think the car could be pretty good over a quarter mile, its already ran 11.4 at 131mph on 19psi on low profile road rubber so im hoping with the drag tyres ive ordered and 30psi+ we could get mid 10s

You dont need to replace the head every time, but after a few builds it may require a skim. Eventually yes though, you run out of skims lol

But absolutely any type of ring system is hit or miss and can take a few goes to get right, as there is no generic ring, groove depth etc etc etc that works for every setup.
In fact, not much difference than your suggestion of running the liners a little proud...getting the height right will also be trial and error and you will probably get it wrong a few times.
Keep an eye on pressure in the cooling system and ensure you've failsafes in place to catch it before anything can cause harm. HG failures with MLS gaskets can tend to do a lot of damage.

And a car at that weight and if it has 500hp+ should be doing 9's nevermind mid 10's

Surely some of the Honda engines wouldnt be much heavier ? And undoubtedly more proven with good power boosted builds ?

[Ive]

http://www.youtube.com/watch?v=_Uzwp4MlxRY&t=3...

500+Hp turbo K20 in a s2000. They post time attack after time attack video.

Goes like stink. In a Elise with aero, it would be a nice powerplant.

Sorry Lee, couldn't resist. I hope you don't mind.
These folks manage to capture the sound of a high reving turbo really well.

I am sure your's also sounds really mean. I am looking forward seeing more.

Regarding distortion of the block, it might be interesting to also take the increased stiffness of the nodular iron liners into account. I was also running them 5 thou proud BTW:
The engine might deform differently than anticipated now under the load of the long bolts as more force is now transfered though the liners than before with the lamellar spin cast items.

Edited by Ive on Sunday 8th October 08:36

[DVandrews]

You can prevent dig in from a triangular ring or wills ring using a shim. that will lower the CR a tad but that isn’t necessarily a bad thing. My experience with wills rings on Imp/FWM(A) Coventry climax engines showed them to be very tricky to get right.

Dave

[Evoluzione]

stevieturbo said:

HG failures with MLS gaskets can tend to do a lot of damage.

I too would just start off with a more suitable engine for these power levels.

Purely for discussions sake, can you expand on your thoughts, causes and experiences on that ^^ ?
I'm thinking if the cause was detonation then the SS gaskets resists it quite well so it takes an alternative path.

Out of interest I've got an engine in bits at the moment (not one of mine) which was mapped by the same outfit that melted the chaps with the V6 Stratos replica, you will remember that one. Lots of det' damage as you can imagine and they lock the ECU so you can't see exactly where they've gone wrong even though the evidence is in your hands.

[Evoluzione]

DVandrews said:

You can prevent dig in from a triangular ring or wills ring using a shim. that will lower the CR a tad but that isn’t necessarily a bad thing. My experience with wills rings on Imp/FWM(A) Coventry climax engines showed them to be very tricky to get right.

Dave

Isn't the fact that it digs in the same feature that makes it work? If you're stopping it from doing that then you are preventing it from working as it should (in theory!). If not they would just make them with flat faces to begin with.

You sometimes wonder if these uprated gaskets are trying to stop something we shouldn't be fighting anyhow - detonation.

[turbotoaster]

stevieturbo said:

You dont need to replace the head every time, but after a few builds it may require a skim. Eventually yes though, you run out of skims lol

But absolutely any type of ring system is hit or miss and can take a few goes to get right, as there is no generic ring, groove depth etc etc etc that works for every setup.
In fact, not much difference than your suggestion of running the liners a little proud...getting the height right will also be trial and error and you will probably get it wrong a few times.
Keep an eye on pressure in the cooling system and ensure you've failsafes in place to catch it before anything can cause harm. HG failures with MLS gaskets can tend to do a lot of damage.

And a car at that weight and if it has 500hp+ should be doing 9's nevermind mid 10's

Surely some of the Honda engines wouldnt be much heavier ? And undoubtedly more proven with good power boosted builds ?

the rover heads are pretty soft and get pretty porous so finding heads that arnt skimmed to death is already starting to become harder.

I currently run my liners at 8 thousand proud which seems to be working at the moment, but i have no idea if that will work if we want to turn it up further, suck it and see as you say, i also run a 0.3mm shim between the gasket and the head to try and protect it.

a honda k20 and gearbox is about 185kg, the rover k series and gearbox is about 120kg, so there is the weight penalty, the honda has potential for alot more power of course.

its never going to be a competitive drag car, the mid 11 was my 3rd ever pass with the car so i dont have the setup time to make an accurate assessment of the potential, but it couldnt race against the jap fwd cars as its not eligable and the rwd/4wd guys will have double the power so i wouldnt be competitive. running a 9 would be amazing but i dont think i could get it to run that fast, i think a mid 10 should be doable with practice.

The car is designed for track use so 600bhp+ isnt needed....but that go at drag racing was alot of fun and im to competitive for my own good!

I did wonder about the O ring option but if the head will want to lift from simply not having the bolt stiffness to hold it down i cant see it working

[turbotoaster]

One of the biggest issues is that I am a guinee pig on this engine.

Im around 7bhp of the most powerful rover k series ive ever heard of and he went the rotrex route so the specifications arent really comparable.

Its nice to push the boundaries as the build up to yet hasnt been massively expensive, but on the other hand it would be nice to have a 600bhp 4g63 in the back where you can buy a proven parts list without even giving it a second thought

[anonymous-user]

Knocking pressure doesn't lift heads. The cyclic knocking pressure, that occurs at something like 5 to 9 Khz depending on chamber geometery is way too quick to overcome the inertia of the head.

Peak combustion pressure is the issue. And good news, you are running a turbo engine, so are not, fundamentally 'air limited' hence the trick is to run more boost and less spark (retarded from MBT), meaning a wider (spread over a greater crank angle) but less spiky cylinder pressure trace, deliberately limiting the peak cylinder pressure achieved.






Of course, this puts increased thermal loads into your exhaust line components (due to the lower overall expansion ratio), but you could counter that either with overfuelling, or better, with water injection (but don't advance the spark and use the WI to make more power, use it to just limit EGT!)

You end up with a less efficient engine (it's BSAC and BSFC are reduced) but you make the same flywheel power.

Edited by anonymous-user on Sunday 8th October 12:17

[turbotoaster]

Max_Torque said:

Knocking pressure doesn't lift heads. The cyclic knocking pressure, that occurs at something like 5 to 9 Khz depending on chamber geometery is way too quick to overcome the inertia of the head.

Peak combustion pressure is the issue. And good news, you are running a turbo engine, so are not, fundamentally 'air limited' hence the trick is to run more boost and less spark (retarded from MBT), meaning a wider (spread over a greater crank angle) but less spiky cylinder pressure trace, deliberately limiting the peak cylinder pressure achieved.






Of course, this puts increased thermal loads into your exhaust line components (due to the lower overall expansion ratio), but you could counter that either with overfuelling, or better, with water injection (but don't advance the spark and use the WI to make more power, use it to just limit EGT!)

You end up with a less efficient engine (it's BSAC and BSFC are reduced) but you make the same flywheel power.

Edited by Max_Torque on Sunday 8th October 12:17

I saw this a while back which i found interesting.



10:1, 14psi and 35deg vs 8:1, 28psi and 25deg

Both have the similar peak cylinder pressures, but the average overall pressure on the low comp engine is higher, hence more power

I assume this is what your talking about, at the moment we hit MBT at peak torque(360ftlbs) at 15 degrees, not sure how that will change when we go for over 30psi