Turbocharging a 2 litre BF18 engine
Discussion
You know that engine in the renault 19, volvo400 series etc... well it comes in a variety of flavours 1.6 to 2.0 turbo1.7only, na and diesel.
Attempts to use the turbo set up head and 2 litre bottom have been thwarted due to heat build up. Allegedly (JuTu) the space between the cylinders is insufficient to dissipate the heat on 0.75bar forced induction and pop! (although nature of said pop is unclear, l am assuming a warped head rather than detonation damage)
Any suggestions that might ameliorate/avoid this?
Attempts to use the turbo set up head and 2 litre bottom have been thwarted due to heat build up. Allegedly (JuTu) the space between the cylinders is insufficient to dissipate the heat on 0.75bar forced induction and pop! (although nature of said pop is unclear, l am assuming a warped head rather than detonation damage)
Any suggestions that might ameliorate/avoid this?
is this on a bench or tested in car?
what coolant did you use(dont say just water)
what ignition mods have been done?
did you use a modified head gasket?
did the engine overheat or did it die and then you think its due to heat?
oil cooler?
did the pistons melt or was it simple head gasket failure?
did it run ok at lower boost?
more info please
what coolant did you use(dont say just water)
what ignition mods have been done?
did you use a modified head gasket?
did the engine overheat or did it die and then you think its due to heat?
oil cooler?
did the pistons melt or was it simple head gasket failure?
did it run ok at lower boost?
more info please
Has the block been "o"ringed? If not and its the gasket thats gone, this modification usually retains the gasket without blow-out problems.
Alternative would be a steel head gasket maybe?
Also whats the Cr with the new head?
If youre tryin to run 0.75bar(11psi) with say 10:1 cr its gonna cause you probs (detonation)if the original setup was lower.
Just a thought.
Alternative would be a steel head gasket maybe?
Also whats the Cr with the new head?
If youre tryin to run 0.75bar(11psi) with say 10:1 cr its gonna cause you probs (detonation)if the original setup was lower.
Just a thought.
I'll second deltaf's suggestion of compression ratio.
Most turbo'ed cars use lower compression ratios, and just mating a head to the bottom end may be causing the problem.
I know that when using a pinto cosworth sans turbo, the CR needs to be increased so I would guess the converse is true the other way round.
Sparks
>> Edited by sparks on Monday 23 December 18:24
Most turbo'ed cars use lower compression ratios, and just mating a head to the bottom end may be causing the problem.
I know that when using a pinto cosworth sans turbo, the CR needs to be increased so I would guess the converse is true the other way round.
Sparks
>> Edited by sparks on Monday 23 December 18:24
Running 11psi would just about be acceptable with standard CR provide such standard was no higher than about 10.5:1 - however, high octance fuel (superplus) and several degress of ignition retard would be required. Modern engine managment systems are very clever when it comes to this and can mess about with retard whilst running. For ultra high boost, the CR needs to be lower than 8:1, however off boost running would be sluggish. Uprated gaskets - especially the "ringed" versions tend to be thicker, so reducing the CR.
With highish boost hence high in-cylinder pressures and narrow cylinder wall thickness, bore flex can be a problem, wich can ulimately result in failure. This can be preceded by high oil consumption and boost limitation. With 11 psi, heat generation from cylinder pressures wouldnt be the problem, it would more likley be incorrect timing, causing detonation. If you could get a look at the plugs and the electrodes appear white and glazed, you'll need to sort the ignition timing or richen the mixture.
Merry christmas.
J.
With highish boost hence high in-cylinder pressures and narrow cylinder wall thickness, bore flex can be a problem, wich can ulimately result in failure. This can be preceded by high oil consumption and boost limitation. With 11 psi, heat generation from cylinder pressures wouldnt be the problem, it would more likley be incorrect timing, causing detonation. If you could get a look at the plugs and the electrodes appear white and glazed, you'll need to sort the ignition timing or richen the mixture.
Merry christmas.
J.
Thanks for all your replies given l have provided so little info. I'm still waiting for some response to some Q's. (This is not my project but it was something l was hoping to pursue in the near future)
The 2 litre head would have been a 10.5:1 CR but l would have expected that this was lowered! CR on these engines under forced induction are typically 8.5. Also the boost would definitely not have been running above 11psi. From what little info l have so far, it appears the problem arises after sustained bouts of hard driving (racing?).
Will add more when l hear more. Thanks again.
The 2 litre head would have been a 10.5:1 CR but l would have expected that this was lowered! CR on these engines under forced induction are typically 8.5. Also the boost would definitely not have been running above 11psi. From what little info l have so far, it appears the problem arises after sustained bouts of hard driving (racing?).
Will add more when l hear more. Thanks again.
Well bollox to them, guess they only respond if you going to buy something. I am going ahead with the 2.0 conversion. I have sourced a bottom end and have asked an engine builder if he would entertain the experiment.
So far l know the following:
1.7 turbo head fits straight on the 2 ltr bottom. Cambelt is the same, engine mounts, gearbox connection are the same. Oil return pipe may need drilling into the sump for the turbo.
I want the engine rebuilt, so:
Compression lowered from 10 to 8.5 (Will this essentially also increase the capacity or is it measured only by swept volume?)
Rings, what type?
Pistons. Eutectic pistons? Ceramic coating? (Good thread that)
Crank. The crank has a larger rotational circumference than the 1.7. I am trying to work out how that will affect torque and power curves, but l am totally unsure!
The injection system is LH2 jetronic, with an air MASS meter so it should be fairly adaptable.
So apart from the usual strengthening, lightening, balancing and tolerances etc... What do l need to consider, have l missed something critical?
At this point anything specific or general would be extremely welcome.
Dan
So far l know the following:
1.7 turbo head fits straight on the 2 ltr bottom. Cambelt is the same, engine mounts, gearbox connection are the same. Oil return pipe may need drilling into the sump for the turbo.
I want the engine rebuilt, so:
Compression lowered from 10 to 8.5 (Will this essentially also increase the capacity or is it measured only by swept volume?)
Rings, what type?
Pistons. Eutectic pistons? Ceramic coating? (Good thread that)
Crank. The crank has a larger rotational circumference than the 1.7. I am trying to work out how that will affect torque and power curves, but l am totally unsure!
The injection system is LH2 jetronic, with an air MASS meter so it should be fairly adaptable.
So apart from the usual strengthening, lightening, balancing and tolerances etc... What do l need to consider, have l missed something critical?
At this point anything specific or general would be extremely welcome.
Dan
Hi, I see a problem here straight away m8.
I presume the 1.7 has a shorter throw?
If thats so then when you put the 1.7 head on the 2 litre, youll be raising the cr, because youre trying to force the larger swept volume into the same chamber volume.
You need to find out what the combustion chamber volume is for both heads in order to make a decision on pistons.
If the volume is going to force a cr change upwards, then go for a set of pistons with a dish to lower it to an acceptable level.
8-8.5 :1 is ok, just use a good intercooler, or chargecooler even.
Change the rod bolts for ARP items.
Air flow meter may handle the change, but possible injectors not, also mapping wont be right, but will run at lower boost levels.
Also a rise in fuel pressure may accomplish the extra fuel requirements, depending on boost used.
Ya need to work out the airflow rates at full boost and revs to make a decision on whether the fuel flow is sufficient at those rates.
Oh and dont forget to check for piston to valve contact, dont let them get any closer than 50 thou or else at revs you can get them touching...not good!
>> Edited by deltaf on Sunday 26th January 15:32
I presume the 1.7 has a shorter throw?
If thats so then when you put the 1.7 head on the 2 litre, youll be raising the cr, because youre trying to force the larger swept volume into the same chamber volume.
You need to find out what the combustion chamber volume is for both heads in order to make a decision on pistons.
If the volume is going to force a cr change upwards, then go for a set of pistons with a dish to lower it to an acceptable level.
8-8.5 :1 is ok, just use a good intercooler, or chargecooler even.
Change the rod bolts for ARP items.
Air flow meter may handle the change, but possible injectors not, also mapping wont be right, but will run at lower boost levels.
Also a rise in fuel pressure may accomplish the extra fuel requirements, depending on boost used.
Ya need to work out the airflow rates at full boost and revs to make a decision on whether the fuel flow is sufficient at those rates.
Oh and dont forget to check for piston to valve contact, dont let them get any closer than 50 thou or else at revs you can get them touching...not good!
>> Edited by deltaf on Sunday 26th January 15:32
I can't for the life of me remember what they call it, but the head is flat. There is not combustion chamber formed by the head itself only by the tops of the piston.
CR for 2.ltr is 9.8
CR for 1.7turbo is 8.1
Throw (presume stroke)
83.5mm Vs 93.0mm.
Could l not use piston head shape to get some nice proven combustion chamber form whilst reducing CR? Seen pistons with depressions expressly for the valves to fit into. (perhaps these are non-interference only and are pants performance-wise)
The airflow is a hotwire air mass sensor. I shouldn't think it'll have any real problems as it IS already turbocharged. Fuelling could be an issue coupled with other modifications. Though about upping fuel pressure and larger injectors, bringing the whole lot back to earth with a fuel chip remap (seperate chips on this engine) so l don't run rich all the time when not on full throttle.
How do l go about finding some custom pistons chumrade?
CR for 2.ltr is 9.8
CR for 1.7turbo is 8.1
Throw (presume stroke)
83.5mm Vs 93.0mm.
Could l not use piston head shape to get some nice proven combustion chamber form whilst reducing CR? Seen pistons with depressions expressly for the valves to fit into. (perhaps these are non-interference only and are pants performance-wise)
The airflow is a hotwire air mass sensor. I shouldn't think it'll have any real problems as it IS already turbocharged. Fuelling could be an issue coupled with other modifications. Though about upping fuel pressure and larger injectors, bringing the whole lot back to earth with a fuel chip remap (seperate chips on this engine) so l don't run rich all the time when not on full throttle.
How do l go about finding some custom pistons chumrade?
Try these, hopefully therell be something here for ya.
www.primaracing.com/engine.htm
www.k-tecracing.com/products.htm
www.volvospeed.com/
www.eurosporttuning.com/home.htm
www.rosspistons.com/
www.ariaspistons.com/
www.jepistons.com/
http://bmeltd.com/pistons.htm
www.mahleinc.com/
www.primaracing.com/engine.htm
www.k-tecracing.com/products.htm
www.volvospeed.com/
www.eurosporttuning.com/home.htm
www.rosspistons.com/
www.ariaspistons.com/
www.jepistons.com/
http://bmeltd.com/pistons.htm
www.mahleinc.com/
Can someone please tell me the best way to reduce CR other than thicker gaskets.
Different pistons perhaps, but what if the current pistons are already dished?
Reducing the throw with a different crank, would also reduce the capacity though wouldn't it? Do l have any real choices here?
Different pistons perhaps, but what if the current pistons are already dished?
Reducing the throw with a different crank, would also reduce the capacity though wouldn't it? Do l have any real choices here?
The bore is wider by a good couple of mm between the 1.7 and 2ltr engines: 81mm Vs 82.7mm so unless l use the 1.7 block, 1.7 pistons, with the 1.7 crank... 
hang on that's the stock set up!
Go on, just tell me l haven't got a hope, l can take it.
Can l assume that because the pistons are already dished to create the combustion chamber l am much less likely to be able to bring CR down by piston choice alone?
hang on that's the stock set up! Go on, just tell me l haven't got a hope, l can take it.
Can l assume that because the pistons are already dished to create the combustion chamber l am much less likely to be able to bring CR down by piston choice alone?
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