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High CR and boosting, how much?
Craigorypeck - 14/8/12 at 10:27 PM

I built my YB to run fast road NA, has approx 11.8:1 CR but I stuck an eaton on for the craic, pushes 5psi and the timing has been retarded way back from na setting to 18 degrees from 4500 to 7500 rpm to avoid pinking, but it seems to boil coolant every time i give it some prolonged beans, especially in higher gears .. can potter about with no probs but any hard right foot and its a jacuzzi under the bonnet. My guess is the timing being that retarded is causing hot spots around exhaust valves and boiling coolant?? or am I getting the wrong idea all together!? pointers please. Ta

coyoteboy - 14/8/12 at 10:49 PM

Might not help being too retarded. Also, if you push 5psi you're pushing 1/3 extra power so you have 1/3 extra heat to remove. TBH I just wouldn't bother boosting a high CR engine because they're generally very hard to get right on a budget due to the very high dynamic CR. That said, good luck!

[Edited on 14/8/12 by coyoteboy]

[Edited on 14/8/12 by coyoteboy]

Oddified - 15/8/12 at 07:21 AM

Are you sure it's not just the head gasket that's gone and the extra power/boost from the super charger has finished it off? (or making it obvious).

18deg timing isn't that low to cause any issues.

Ian

Craigorypeck - 15/8/12 at 07:49 AM

You may be right but I checked with a rad pressure tester and its holding its pressure..? tested on hot and cold engine. I might get the lend of a CO2 sniffer test aswell, will do a compression test too.

would my head gasket be under a lot of strain with upped CR and a 5psi of boost?? more so than a standard YB cosworth with low CR pistons but more boost??

[Edited on 15/8/12 by Craigorypeck]

Oddified - 15/8/12 at 02:17 PM

Not really more strain, but if the gasket was a bit marginal before fitting the supercharger, then the extra cylinder pressures would make it worse. Quite often a gasket that's only just started to go will only really leak when under maximum pressure/load (ie, giving the car some stick) and when driven normaly will seem fine. Over time the problem gets worse and water being blown out happens on less throttle.

Which head gasket is fitted now?.

Ian

Craigorypeck - 15/8/12 at 04:09 PM

Hi, there's a reinz standard yb one In, from buttons I think, looked like decent item with metal between the bores.

Oddified - 15/8/12 at 04:49 PM

I know the one, as it's what i used to use on mine.

Absolutely fine until you start hitting it with some extra power, in my case nitrous (over 100bhp extra). When it had gone, it would be fine running around normaly, use nitrous and it would empty the water out on the floor. I found they'd last 2 or 3 rwyb meetings and then start blead pressure into the water under full load. I always found that they'd not blow as such with a chunk missing, but there would be spider legs (for want of a better description!) from the cylinders leading to the water jackets.

I've now been using a Cometic mls gasket for a few a years now, with no coolant issues at all since.

Ian

Craigorypeck - 15/8/12 at 09:02 PM

oh dear, you could be right enough, also getting what I'd call more than enough vapour from the crank case breather too. Are you using nut and stud head bolts??

also are those cometic ones the 5 layer metal jobs??

[Edited on 16/8/12 by Craigorypeck]

Oddified - 16/8/12 at 07:37 AM

quote:
Originally posted by Craigorypeck
Are you using nut and stud head bolts??


Yes i use an ARP stud kit on mine. I tried those first to help the head gasket but the only thing that stopped it was a cometic mls.

If your running 11.8 comp, then i guess you'll probably have forged pistons fitted (Accralite or similar) which means the piston-bore clearance is greater. Any of the more modern weasel pi$$ engine oils breath a lot/leak, i found that Valvoline VR1 20/50 works very very well in these engines.

Ian

Craigorypeck - 16/8/12 at 04:59 PM

yes accralite pistons and I'm using halfords 15-40 semi synthetic, i was under the impression their oil was as good as any others because of strict consumer protection?

do the multi layer steel ones need a particular finish on the mating surfaces?? ie could i just whip off the head give it a clean and thro a multi layer in and it will work as should??

Thanks

[Edited on 16/8/12 by Craigorypeck]

coyoteboy - 16/8/12 at 06:55 PM

Halfords oil to the correct spec is perfectly fine, but if you're over-stressing the engine comparend to standard operation you might want to consider a better rated oil, and maybe change of weight profile etc. If you're regularly seeing higher running temps than in normal operation your oil could be losing too much viscosity, a higher weight on the top end should help, but bear in mind that oils with a big weight range tend to die faster (the polymers used to ensure the large viscosity range degrade with heat and age).

As for MLS - they're less forgiving than normal gaskets - you want the surface CLEAN and you want to ensure the mating surfaces are true to the spec suggested by the gasket manufacturer, not the engine manufacturer.

[Edited on 16/8/12 by coyoteboy]

Craigorypeck - 16/8/12 at 08:18 PM

Ok, thanks for that, will get on it soon.

BaileyPerformance - 20/8/12 at 10:11 AM

I would say 18deg is still alittle bit too much timing, i know your not running much boost but the high static CR will bring on the det quickly which you cant always hear in a noisy car.

As stated before i wouldn't think the retarded timing is effecting the cooling system, i have seen 550bhp ybs at 4-6deg timing without overheating. (but with big ally rad)

If the engine has been run with mild det it could have damaged the head gasket causing your problem, from past experience the stock yb gasket (we only used Ford ones) is good for 25PSI but at standard CR. Ignition timing was around 8 deg at max boost. 16deg at idle.

Does the car seem slower at less timing?

What is your AFR at full throttle?

What is the engine temp when it starts to boil?.....do the hoses seem hard?

Craigorypeck - 20/8/12 at 11:19 PM

Hi there, The temp gauge goes up but not a lot, i do have the temp sender at the rear of the engine where the coolant comes in after the heater box, not the best place for it tbh as is not a real indication? hoses are hard after a run.
Afr at full throttle is around 12:1 never leaner.
I did tune the timing myself whilst driving and there was some pinking but never sustained, always backed off and lowered, but still it did receive some pinking time in the process.
I think its defo a gasket issue

Craigorypeck - 25/8/12 at 09:05 PM

Block is cracked in 2 places, water is getting to oil.

Wanted 205 block!

mcerd1 - 26/8/12 at 03:55 PM

maybe this is the time to upgrade to one of those fancy motorsport or alloy blocks that burtons sell

Craigorypeck - 26/8/12 at 05:21 PM

Aaaaaaaaahahahahaha! with the amount i can spend it might get a standard 2.0 non 205 block @ >£50

mcerd1 - 27/8/12 at 12:00 PM

quote:
Originally posted by Craigorypeck
Aaaaaaaaahahahahaha! with the amount i can spend it might get a standard 2.0 non 205 block @ >£50


I've got a couple of them with pistons stuck in them you could have for nowt

laptoprob - 24/11/12 at 09:09 AM

I know the post is a few months old but nobody really answered the question origianlly.

Any of you tech gurus have the definitive naswer.....can you boost a high comp engine,say 12 or 13:1?

bi22le - 24/11/12 at 10:19 AM

Its seems that potentially yes but the risks and chances of failure are high.

jeffw - 24/11/12 at 10:44 AM

I'm running 11.5:1 with 15psi at the redline. Zetec with a Rotrex

BaileyPerformance - 24/11/12 at 11:46 AM

quote:
Originally posted by laptoprob
I know the post is a few months old but nobody really answered the question origianlly.

Any of you tech gurus have the definitive naswer.....can you boost a high comp engine,say 12 or 13:1?


Depends on the cam profile and engine design, its not just static CR and boost pressure that's important is the effective CR. The effective CR (the actual pressure inside the cylinder) and the shape of the combustion chamber decides how much an engine will take before it detonates.

If you have and engine thats running 15PSI of boost it does not mean all that boost if finding its way into the cylinders, most of it will get in there at low RPM (assuming you can make boost a low RPM that is) but as the RPM rises the boost pressure in the cylinder will reduce. This is due to inlet/head/cam restricting airflow.

Decent engine such as a cosworth YB the head design is very good as standard, so the engine will make good power at low boost pressures, as the boost pressure is increased (in the hope of gaining more power) the law of diminishing returns comes in, for example a stock YB will make around 270BHP at 15PSI but it will not make 540BHP at 30PSI (without further breathing mods) so it is clear not all the boost is finding its way into the cylinders.

Ultimately its detonation thats the overriding factor when chasing big power, a simple way to keep the engine out of det is lower the static CR, this slows down the flame front and reducing combustion temps helping to reduce det. The negative effect of a low CR is the fact it reduces the engine's efficacy by not making the "best use" of the the fuel, the EGT is much higher on a low CR engine than on a high CR engine as there is more wasted energy on the low CR engine.

If its massive BHP your after (500BHP+) then a CR or around 9/1 is as high as you can go on pump fuel, but 300-400BHP on a zetec or YB is best achieved with a high CR as this makes the engine better on fuel and gives much better throttle response.

It is possible to run very high CR's on a turbo/SC engine if the right cams are used and timing in to suit, normally an engine is most likely to knock at peak torque, the effective CR can be reduced by selecting a cam with quite high overlap, this bleeds some boost down the exhaust reducing the pressure in the cylinder - but when the high RPM is used a cam like this will come into its own and really make the engine breath making much more power than a standard short duration cam. We have used full race NA cams in turbo engine and made some big numbers on the dyno, but be warned the ignition timing and fuelling MUST BE SPOT ON AT ALL TIMES otherwise you will end up with bits of engine on the floor!!

jeffw - 24/11/12 at 12:50 PM

I should say that 15psi comes out of the Rotrex but only 9psi arrives at the plenum as 6psi is eaten by the intercooler (which is rubbish I know). The car makes 300HP/250 ft lb at the wheels.

MRLuke - 24/11/12 at 04:00 PM

quote:
Originally posted by BaileyPerformance
Decent engine such as a cosworth YB the head design is very good as standard, so the engine will make good power at low boost pressures, as the boost pressure is increased (in the hope of gaining more power) the law of diminishing returns comes in, for example a stock YB will make around 270BHP at 15PSI but it will not make 540BHP at 30PSI (without further breathing mods) so it is clear not all the boost is finding its way into the cylinders.


Do you not have to consider that 15psi is actually 15psi above atmospheric (as at 0psi boost engine will still make power) Therefore you are going from circa 30psi total to 45psi total. Gives power of about 400bhp which probably isnt far off what a cossie makes on 2bar?

BaileyPerformance - 24/11/12 at 09:26 PM

quote:
Originally posted by MRLuke
quote:
Originally posted by BaileyPerformance
Decent engine such as a cosworth YB the head design is very good as standard, so the engine will make good power at low boost pressures, as the boost pressure is increased (in the hope of gaining more power) the law of diminishing returns comes in, for example a stock YB will make around 270BHP at 15PSI but it will not make 540BHP at 30PSI (without further breathing mods) so it is clear not all the boost is finding its way into the cylinders.


Do you not have to consider that 15psi is actually 15psi above atmospheric (as at 0psi boost engine will still make power) Therefore you are going from circa 30psi total to 45psi total. Gives power of about 400bhp which probably isnt far off what a cossie makes on 2bar?


Your probably right, a cossy would make 400BHP ish at 2bar, but that's what i said - 30PSI (2bar) it would not make twice the power it did at 15PSI (1bar).

The term "boost" infers extra air over an above what the engine can pull in on its own "naturally aspirated". I good race engine will achieve a VE of 95%, F1 maybe over 100% due to cleaver ram effect, average production car engine probably around 80%. The higher the VE the higher the effective compression and more power. So its not true to say 15PSI of boost is actually 30PSI as that would suggest the engine has a VE of 100% before you turbo charge it, which is not likely.

Boost is always quoted gauge not absolute - but the engine management measures absolute (MAP) as it needs to read vacuum for load purposes when off boost as well as on boost.

BaileyPerformance - 24/11/12 at 09:35 PM

quote:
Originally posted by jeffw
I should say that 15psi comes out of the Rotrex but only 9psi arrives at the plenum as 6psi is eaten by the intercooler (which is rubbish I know). The car makes 300HP/250 ft lb at the wheels.


Thats really really good power for that boost, you must have decent cams to make that sort of power. We see around 330BHP (at engine) at 20PSI but that's with stock head and cams, we normally see more torque than power (this is due to the stock cam profile)

As you say the intercooler seems to be dropping alot, but a cool charge maybe worth more to your engine than boost, considering you have a high CR.

On a zetec a 10deg drop in air temp is worth the same as a couple of pounds of boost, so if you replaced your intercooler with a free-flow version the chances are the boost would go up and so would the air temp, you could end up with less power!!

Have you got the cam spec please? just out of interest.

MRLuke - 24/11/12 at 10:00 PM

quote:
Originally posted by BaileyPerformance
quote:
Originally posted by MRLuke
quote:
Originally posted by BaileyPerformance
Decent engine such as a cosworth YB the head design is very good as standard, so the engine will make good power at low boost pressures, as the boost pressure is increased (in the hope of gaining more power) the law of diminishing returns comes in, for example a stock YB will make around 270BHP at 15PSI but it will not make 540BHP at 30PSI (without further breathing mods) so it is clear not all the boost is finding its way into the cylinders.


Do you not have to consider that 15psi is actually 15psi above atmospheric (as at 0psi boost engine will still make power) Therefore you are going from circa 30psi total to 45psi total. Gives power of about 400bhp which probably isnt far off what a cossie makes on 2bar?


Your probably right, a cossy would make 400BHP ish at 2bar, but that's what i said - 30PSI (2bar) it would not make twice the power it did at 15PSI (1bar).

The term "boost" infers extra air over an above what the engine can pull in on its own "naturally aspirated". I good race engine will achieve a VE of 95%, F1 maybe over 100% due to cleaver ram effect, average production car engine probably around 80%. The higher the VE the higher the effective compression and more power. So its not true to say 15PSI of boost is actually 30PSI as that would suggest the engine has a VE of 100% before you turbo charge it, which is not likely.

Boost is always quoted gauge not absolute - but the engine management measures absolute (MAP) as it needs to read vacuum for load purposes when off boost as well as on boost.


At 0psi boost the engine is making around 130bhp. You are increasing the mass of air by 50% so the power should increase by 50% as well not 100% as your post reads.

There will be losses whether its is FI or not but I think that talking about VE is just over complicating something that doesn't warrant it.

BaileyPerformance - 24/11/12 at 10:18 PM

quote:
Originally posted by MRLuke
quote:
Originally posted by BaileyPerformance
quote:
Originally posted by MRLuke
quote:
Originally posted by BaileyPerformance
Decent engine such as a cosworth YB the head design is very good as standard, so the engine will make good power at low boost pressures, as the boost pressure is increased (in the hope of gaining more power) the law of diminishing returns comes in, for example a stock YB will make around 270BHP at 15PSI but it will not make 540BHP at 30PSI (without further breathing mods) so it is clear not all the boost is finding its way into the cylinders.


Do you not have to consider that 15psi is actually 15psi above atmospheric (as at 0psi boost engine will still make power) Therefore you are going from circa 30psi total to 45psi total. Gives power of about 400bhp which probably isnt far off what a cossie makes on 2bar?


Your probably right, a cossy would make 400BHP ish at 2bar, but that's what i said - 30PSI (2bar) it would not make twice the power it did at 15PSI (1bar).

The term "boost" infers extra air over an above what the engine can pull in on its own "naturally aspirated". I good race engine will achieve a VE of 95%, F1 maybe over 100% due to cleaver ram effect, average production car engine probably around 80%. The higher the VE the higher the effective compression and more power. So its not true to say 15PSI of boost is actually 30PSI as that would suggest the engine has a VE of 100% before you turbo charge it, which is not likely.

Boost is always quoted gauge not absolute - but the engine management measures absolute (MAP) as it needs to read vacuum for load purposes when off boost as well as on boost.


At 0psi boost the engine is making around 130bhp. You are increasing the mass of air by 50% so the power should increase by 50% as well not 100% as your post reads.

There will be losses whether its is FI or not but I think that talking about VE is just over complicating something that doesn't warrant it.


My power example was based on a cosworth YB, which will not make more than 100BHP in NA form assuming the engine is stock, we have seen a stock YB in a car just with turbo removed and carbs fitted and they make less power than a pinto.

So, the folks at Ford designed the cosworth YB to make around 210BHP, at 8psi so the turbo doubled the engines power output at only half a bar, at 1bar you only get another 60BHP.

So to state "You are increasing the mass of air by 50% so the power should increase by 50% as well" is wrong, it all depends on the engines VE. The VE depends on engine breathing and CR.

jeffw - 25/11/12 at 05:22 AM

quote:
Originally posted by BaileyPerformance
quote:
Originally posted by jeffw
I should say that 15psi comes out of the Rotrex but only 9psi arrives at the plenum as 6psi is eaten by the intercooler (which is rubbish I know). The car makes 300HP/250 ft lb at the wheels.


Thats really really good power for that boost, you must have decent cams to make that sort of power. We see around 330BHP (at engine) at 20PSI but that's with stock head and cams, we normally see more torque than power (this is due to the stock cam profile)

As you say the intercooler seems to be dropping alot, but a cool charge maybe worth more to your engine than boost, considering you have a high CR.

On a zetec a 10deg drop in air temp is worth the same as a couple of pounds of boost, so if you replaced your intercooler with a free-flow version the chances are the boost would go up and so would the air temp, you could end up with less power!!

Have you got the cam spec please? just out of interest.


The cams are designed by CNC Heads (http://www.cncheads.co.uk/?p=755) to work with their head. The cams have the maximum lift you can get away with on stock pistons so something more than Piper 285 but not full race cams. The engine made 190HP at the wheels NA.

BaileyPerformance - 25/11/12 at 03:45 PM

Thanks for that, i'll have a look.

Your using stock pistons? the standard Ford items? that surprises me.

I think the most we have seen out of a NA 2.0L zetec is about 190BHP at the flywheel, so you are doing well to get 190 at the wheels - that must be at least 210 at the engine? did your tuning give you a engine and wheel printout?

jeffw - 25/11/12 at 06:03 PM

NA was stock pistons and rods...it now has forged pistons and rods as you would expect as well as ARP studs.