Different tq/hp output for XRR/FXR (inline vs flat)

[bw_krupp]

If I remember correctly, a flat engine of the same size tends to rev less and produce more torque than its inline brother. Hence it would be nice to see that reflected ingame as well. If corrected this would also provide a nice balance to the GTR cars:
FZR - lightest, highest revving, least torque
XRR - medium, medium, medium
FXR - heaviest, lowest revving, most torque

[lalathegreat]

that is quite a big generalization

[danowat]

If I remember correctly, a flat engine of the same size tends to rev less and produce more torque than its inline brother

Are you sure on that? :shrug:

AFAIK Flat engines have the advantages of lower centre of gravity and less vibration / balancing problems

[tristancliffe]

Very very very big generalisation, with almost no truth in any of the statements.

[danowat]

Very very very big generalisation, with almost no truth in any of the statements.

What statements specifically?, care to expand a little more Tristan, share the knowledge an all that :shrug:

[ajp71]

Both the FXR/XRR are turbo charged which means they'll generally be able to produce power lower down and not have to rev so hard with plenty of torque, WRC cars rev to about 5500 and I remember reading somewhere that the Toyota GT1 car only revved to 6500. Of course that's a huge generalization as well it's like saying a turbocharged BDA is low revving.

[tristancliffe]

The torque an engine produces has nothing to do with the layout of the cylinders, but the stroke length (which defines the throw on the crank), the bore, cylinder head design etc. The revs an engine can produce can also be said to be limited by the stroke of the engine, as it defines the piston accelerations (and thus conrod stresses) for a given rpm.

So a long stroke engine (with everything else the same) will produce more crank torque and have a lower rev limit than a short stroke engine (e.g. F1 engines produce almost no torque but rev really really high, whereas truck engines barely rev but produce masses of torque).

However, there is absolutely no reason why a flat engine has to have a longer stroke than an inline engine - you can a long stroke inline 34 cylinder engine, or a tiny stroke flat four. Thus it is a generalisation of enourmous magnitude.

He's probably based his 'assumption' on a Subaru boxer engine which has it roots in 60s engine design) versus some generic hot-hatch engine, and thinks that that must be 'the rule'. It's not!

[wheel4hummer]

So a long stroke engine (with everything else the same) will produce more crank torque and have a lower rev limit than a short stroke engine (e.g. F1 engines produce almost no torque but rev really really high, whereas truck engines barely rev but produce masses of torque).

An example to prove that is to take a very short wrench, and a very long wrench. The stroke of an engine would be you moving your hand. With the long wrench, the 'stroke' is bigger then with the small wrench. Also, it takes longer to move your hand one rotation with the long wrench then it does with the small one.

Another is the Caddilac CTSv-R. That car is powered by a GM V-8 engine. The stroke was actually decreased, and the bore increased. It is only 20ci bigger then the non-race CTSv. It can rev higher than 4cyl engines.... its maximum power is at 7000rpm. 6L, and it can stil rev to >7000rpm.

[jayhawk]

Though not a factor in LFS (or is it?) is the shape and style of the intake manifold can affect torque.

[tristancliffe]

As can the exhaust manifold. Or the shape of the combustion chambers. Or the lack/presence of windage passages, or the angle of the valve seats, or the timing of the camshafts or the........... But this is not in question. The original statement was that Inline 4s are high revving but produce lower torque.

[Bob Smith]

WRC cars rev to about 5500
That's an intentional limit involved in WRC to limit power.

[Primoz]

Isn't the power in WRCs limited with a 34 mm pipe for the turbo intake?

[duke_toaster]

WRC cars are theoretically limited to 300 bhp.

[KeiichiRX7]

anyone else noticed that the first post seems to state that flat engines should be low revving, then turns around and suggests that the FZR with its flat 6 should be the highest revving?

[ajp71]

That's an intentional limit involved in WRC to limit power.

Enforced how exactly? My understanding was they were free to rev higher but given the nature of their engines there is no gain to be had.

[Bob Smith]

I know there's some form of power limiting in WRC, but that's as much as I know.

Perhaps I should have phrased it "There is an intentional limit..."

[tristancliffe]

Isn't the power restriction caused by an obstuction (usually an orifice plate) in the intake system. This reduces the amount of air that can get through, and basically makes high revs (where lots of air is needed) pointless, so they tune the cars for lower revs. It's the same with F3 engine - the restrictor makes anything above 6500rpm useless.

[ajp71]

I think Tristan's probably right any series that tries to limit or class cars by power is floored. Britcar tried to use a system of classing cars by power but given the nature of modern engine mapping flicking a switch can easily loose 100bhp so it was never used, plus the logistics of trying to get 50 cars through an accurate portable rolling road that would have to accommodate for 600bhp cars with bags of torque and potentially 4WD cars.

[tristancliffe]

Ah ha :)


Technical regulations mandate that World Rally Cars must be built upon a production car with a minimum of 2500 units, based on a pre-existing Group A model, to which a number of modifications may be added, including but not limited to increasing engine capacity to 2.0 litres, adding a turbocharger, four wheel drive, active differential, sequential gearbox and aerodynamic apendages.

However, unlike Group A, manufacturers are no longer required to build "Homologation Specials" in order to meet approval. The base model need not have the characteristics of the WRC, as evidenced from cars such the Peugeot 206 and 307, Citroën Xsara, or the Skoda Fabia, which have no road car with a turbocharged petrol engine or four wheel drive.

To limit power, all forced inducted (turbo) cars are fitted with a 34 mm diameter air restrictor before the turbocharger inlet, this limits the air flow to about 10 cubic meters per minute. The restrictor therefore limits the power output to about 330-340 hp (officially 300 hp - which was correct about 10 years ago). Because of that, engine development is more focused on producing an engine with a very wide power curve rather than a high peak power output. This means that a power ouput in excess of 300 hp is availible all the way from 3000 rpm to the red line of 7500 rpm with a peak of 330-340 hp at around 5500 rpm. At 2000 rpm, which is the idle speed in "stage" mode, the power output is slightly above 200 hp [1]. The cars are further modified for greater rigidity with rollcage and other chassis strengthening measures. Before each rally, the competing cars are fitted with suspension and tyres along with different differential settings to suit the conditions of the many stages, which may take place on asphalt roads, gravel and dirt roads of varying consistency, and even frozen snow-covered roads on some rallies held in relatively cold climates.

I was right. 34mm is quite large though, for a 2.0 litre engine. I think F3 has a 25 or 26mm restrictor, also with 2.0 litre engines to give about ~200hp at 6500rpm. The unrestricted engines would just be getting 'on song' about then.

[ajp71]

I was right. 34mm is quite large though, for a 2.0 litre engine. I think F3 has a 25 or 26mm restrictor, also with 2.0 litre engines to give about ~200hp at 6500rpm. The unrestricted engines would just be getting 'on song' about then.

You ever thought of running the engine deristricted? ;)

[tristancliffe]

Yes. But to just remove the restrictor would be a major change - different cams, different ECU maps, different intake/exhaust system, lowering of the compression ratio (it's about 13:1) to suit etc etc. Which is why we are replacing our TOM'S Toyota F3 engine (160hp) with a standard Toyota MR2 3S-GE engine, on carbs, to get about 200hp (and make it eligable for the Monoposto series). We could get more, but the series demands an almost totally standard engine, and it's actually simpler to bolt this one in rather than change the TOM'S engine (which could be worth money to someone else wanting to race in Club F3 or similar).

[ajp71]

Yes. But to just remove the restrictor would be a major change - different cams, different ECU maps, different intake/exhaust system, lowering of the compression ratio (it's about 13:1) to suit etc etc. Which is why we are replacing our TOM'S Toyota F3 engine (160hp) with a standard Toyota MR2 3S-GE engine, on carbs, to get about 200hp (and make it eligable for the Monoposto series). We could get more, but the series demands an almost totally standard engine, and it's actually simpler to bolt this one in rather than change the TOM'S engine (which could be worth money to someone else wanting to race in Club F3 or similar).

Yep in all seriousness if you wanted to run your current engine as a derestricted engine you'd be redesigning it from block up. Are you really sure you're going to be bolting in a standard engine? I always found that statement on the Monoposto site rather weird certainly in the 750 F4 series the engines end up having to be rebuilt in a new spec, even though they're 'standard' you'll end up building the engines much like you would a full race engine just putting more standard/cheapish stuff in.

Doing an engine change isn't simple though, are you sure you're going to be ok with using the current gearbox (and does Monoposto allow 5 speeds?) with the new engine.

Anyway a shameless plug for the 750 F4 series as an alternative to Monoposto which would probably work out slightly cheaper too. Your chassis could be very competitive running a Zetec, and there's always the possibility of buying a competitive engine to save you the time and effort of building one yourself.

http://www.750mc.co.uk/

[tristancliffe]

Nice try ;)

Yes, we are rebuilding the engine, so that we can make sure it's not about to explode, and then dry-sump it, lighten the flywheel etc. And being a Toyota engine of the same family, it will just bolt in using the existing A-frames and bulkhead mountings, and fit the gearbox. Indeed, Mono allows 5-speeds, although we might need a tweak of gearing to make it worthwhile, which is something I've already done the analysis on. As for torque ratings the existing Hewland is fine too :)

I'll have a read about the F4 series in any case!

Edit: Their site doesn't work with FF properly (the menus). Had a look. Have to use a Ford engine, have to use a 4 speed box, have to use control slicks... The technical regulations I think must be the wrong one - it says you have to have metal beam structures in the chassis (we have carbon monocoque), no aerofoils in front of the front wheels etc... so I'm ignoring them for the time being. Quite simply it doesn't sound like the best thing for us - cheaper to use a Toyota engine, the 5 speed 'box and Mono tyres are 'free' too :)

[bw_krupp]

Yea, broad generalizations I know. I was just stating it would be nice to have a difference between the two engines. And I restate what I was intending:
FZR - lightest, highest revving, least torque
XRR - medium, medium, medium
FXR - heaviest, lowest revving, most torque

As for configuration of pistons making no difference, that is false. Why else do some companies agonize over the amount of degrees in the V configuration? A narrow V produces more power higher up and a wider V produces more power down low.

[ajp71]

Edit: Their site doesn't work with FF properly (the menus). Had a look. Have to use a Ford engine, have to use a 4 speed box, have to use control slicks... The technical regulations I think must be the wrong one - it says you have to have metal beam structures in the chassis (we have carbon monocoque), no aerofoils in front of the front wheels etc... so I'm ignoring them for the time being. Quite simply it doesn't sound like the best thing for us - cheaper to use a Toyota engine, the 5 speed 'box and Mono tyres are 'free' too :)

There's a Dallara F3 car (the one that made your chassis redundant overnight) already running with a Zetec so I guess monocoques are allowed. If you already know what you're doing then you'd probably be better going with the Toyota engine, I don't think your car had a stressed engine like modern F3 cars AFAIK, if it does then obviously you'll have either extensively modify the block. If you're sure everything fits then that will be a very good idea to go for, if there are other cars already running similar engines then that'd be great. If, however, you're effectively going on a wing and a prayer and this is a unique conversion then be prepared for a lot of teething problems (be prepared for them anyway) and you'd probably be better off leaving it as it is and taking it historic racing, though it is pricey, or selling it and getting another single seater better suited to your task, also remember a carbon tub seems like a great idea until you bend it, spaceframes can be repaired easily with welding gear and a little know how, oh yeah and tank tape bodywork.

Number one rule is to take it testing and bed it in properly, money well spent, too many people try to skip a simple test session, a race meeting practice session is not a substitute and soon gets expensive when you've spent £250 to find out you've missed something obvious.

The advantage of the Zetecs is they've been widely used so you can go and buy a competitive engine off the shelf (well in theory at least)although that does disadvantage people who don't have as much money to throw at it and they're relatively unstressed and reliable

[tristancliffe]

Sorry, but that is rubbish mate. The amount of torque a cylinder produces is a product of the force acting over the top of the piston and the stroke of the engine. You can invert the cylinder, sit it horizontally, or have it the right way up and it won't make any difference. Stick them all on random orientations in a big line and it still wouldn't make any difference.

What the configuration allows is control of balancing the engine (inline 3s are near perfectly balanced and inline 6s too, which is why V6s and V12s are so smooth. I4s and F4s are pretty horrid balancing wise etc. The other factor is packaging - and I4 and F4s are easy to stick between the front wheels without intruding too much into the passanger compartment. In motorsport it's often CoG that dictates stuff. Renault's F1 engines (recently) have been wide angle to give a lower CoG, at the expense of vibration characteristics. The Vee angle in now way dictated the power/torque of the engine, which I repeat is a function of the bore/stroke (amonst other things).

Perhaps if you compare some engines of the same bore/stroke/combustion chamber/breathing etc you'll see. The best way is to compare F1 engines of different Vees. Data is available showing the Renault engines have tended to have longer strokes and smaller bores, concentrating or torque rather than power (i.e. it revs less because of the longer stroke (and the peak/mean piston speeds thus caused), but the longer stroke gives more torque for a given piston crown force).

So, before making sweeping statements, think.

[tristancliffe]

There's a Dallara F3 car (the one that made your chassis redundant overnight) already running with a Zetec so I guess monocoques are allowed. If you already know what you're doing then you'd probably be better going with the Toyota engine, I don't think your car had a stressed engine like modern F3 cars AFAIK, if it does then obviously you'll have either extensively modify the block. If you're sure everything fits then that will be a very good idea to go for, if there are other cars already running similar engines then that'd be great. If, however, you're effectively going on a wing and a prayer and this is a unique conversion then be prepared for a lot of teething problems (be prepared for them anyway) and you'd probably be better off leaving it as it is and taking it historic racing, though it is pricey, or selling it and getting another single seater better suited to your task, also remember a carbon tub seems like a great idea until you bend it, spaceframes can be repaired easily with welding gear and a little know how, oh yeah and tank tape bodywork.

Number one rule is to take it testing and bed it in properly, money well spent, too many people try to skip a simple test session, a race meeting practice session is not a substitute and soon gets expensive when you've spent £250 to find out you've missed something obvious.

The advantage of the Zetecs is they've been widely used so you can go and buy a competitive engine off the shelf (well in theory at least)although that does disadvantage people who don't have as much money to throw at it and they're relatively unstressed and reliable

Yes, our engine is semi-stressed (A-Frames take some of the load straight to the gearbox, but some is taken by the engine), and yes the mounting points are all the same, so it really is a bolt in job when we've rebuilt it. Might have to make a few new brackets as not every hole is in the same place for ancilliaries, but nothing too major. The biggest 'problem' is that the new crank has a longer nose than the F3 crank, so we're going to have to shorten it and use a narrower pulley (possibly stealing the F3 one for the time being). Not a HUGE problem, but the biggest we face at the moment. Oh, and someone at work distorted the cam cover welding on a few bits - fool!

There's another Toyota powered car in Mono, although he uses a version that has variable valve timing - something banned (even if altered to fixed cam) in Mono - so we're saving that to get him kicked out mid-season if we're vaguely near his points ;)

Don't worry, we're not making it up entirely as we go along. We've found clever people who have done 'similar' things before, or worked on the 3S-GE engine before, or who worked on F3 cars in that era... But not knowing for sure is part of the fun ;)

I'm sure Zetec has a lot going for it. But modifying mountings, changing 'box adaptor plates, changes of wheelbase, cooling system... just a bit too much hassle for us. Maybe one day in the future, when we want a change of scene.

P.S. My ARDS test is booked for the 25th of January, at Silverstone. Yippee!

[ajp71]

Sorry, but that is rubbish mate. The amount of torque a cylinder produces is a product of the force acting over the top of the piston and the stroke of the engine. You can invert the cylinder, sit it horizontally, or have it the right way up and it won't make any difference. Stick them all on random orientations in a big line and it still wouldn't make any difference.

A couple of examples of this are radial engines and IIRC there was a German WW2 reconnaissance aircraft that had an inverted V8 for packing reasons.

[ajp71]

Yes, our engine is semi-stressed (A-Frames take some of the load straight to the gearbox, but some is taken by the engine), and yes the mounting points are all the same, so it really is a bolt in job when we've rebuilt it.

Well I can't quite visualize exactly how that's working but if the engine block is acting as a stressed component of the chassis you really need to check that the new block is ok because normally a stressed engine will require a substantially strengthened block although I guess your car is effectively an unstressed engine because that's what the F3 car running in 750 F4 must be to run a standard Zetec block. What you really don't want to find out though is that the difference between the TOMs block and your new block is that's ones designed to be stressed that would be an expensive mistake ;)

[tristancliffe]

Some amazing TristanArt to help visualise it coming up...

Edit: here it is ;)

http://www.reynard883.com/misc/layout.jpg

Edit2: The damaged monocoque in the picture isn't how it is, but how it might become if I'm let loose in it.

Also, are you looking for a promotion in the sadness ratings?

[Chris_Kerry]

Some amazing TristanArt to help visualise it coming up...

Edit: here it is ;)

http://www.reynard883.com/misc/layout.jpg

Edit2: The damaged monocoque in the picture isn't how it is, but how it might become if I'm let loose in it.

Also, are you looking for a promotion in the sadness ratings?

Drawn with the brilliant artistic flair I've become accustomed to when viewing your work Mr Cliffe.

[ajp71]

Some amazing TristanArt to help visualise it coming up...

Edit: here it is ;)


That looks like an almost fully stressed engine to me, how substantial is that A frame? An unstressed chassis should have a full tub/spaceframe structure with engine mounting at both ends. If the A frame is substantial enough you may find that that could be an unstressed engine but I would have said to find out about it pretty soon. Simply finding out what kind of modifications have been done to the TOMs block should give you a good idea.


Edit2: The damaged monocoque in the picture isn't how it is, but how it might become if I'm let loose in it.


That's reassuring you could do with fitting wheels and suspension is quite a popular option nowadays. If your on a tight budget you may want to skip out the brakes :D

[tristancliffe]

It's a standard 3S block, with no modifications. Or to the block. (Talking about the TOM's stuff). It even has 3S stamped on it, but no corresponding chassis number which indicates it was bought from Toyota as a lone engine rather than pinched out of a car).

The A-Frame tubes are about 3/4" OD. Not sure about ID. I'm guessing they'll be Chrome Moly.

[ajp71]

It's a standard 3S block, with no modifications. Or to the block. (Talking about the TOM's stuff). It even has 3S stamped on it, but no corresponding chassis number which indicates it was bought from Toyota as a lone engine rather than pinched out of a car).


The problem is that modifications to a block are not easily visible and often start with a production block, new or otherwise like the rumored BMW Brabham turbo blocks that were supposedly found lying around outside out of a road car that had done 100000 miles, I don't believe that for a minute but it is possible they started life destined to go in a production car. As for the chassis your best bet would be to confirm that it'll be ok with someone knows about your chassis to do that than end up wrecking a perfectly good block. I guess TOMs probably would remark a modified block being an official part of Toyota and all.

[tristancliffe]

I'll inquire a bit further, but I suspect it'll be fine.

Incidentally, I heard that the Brabham blocks weren't used, but had been sitting for ages doing nothing. Over the years the internal stresses had dissipated, making them ideal for tight tolerence racing. I very much doubt they'd be used (although they'd be rebored and checked thoroughly for cracks/distortion, so maybe they could).

[ajp71]

Incidentally, I heard that the Brabham blocks weren't used, but had been sitting for ages doing nothing. Over the years the internal stresses had dissipated, making them ideal for tight tolerence racing. I very much doubt they'd be used (although they'd be rebored and checked thoroughly for cracks/distortion, so maybe they could).


I suspect in reality they were probably a batch of blocks that *happened* to end up being made of completely different materials.

[KeiichiRX7]

not to be an ass but i believe you gents have jacked a lad's thread

[tristancliffe]

Not entirely. We answered his questions and statements, and put him straight. Whilst we were doing this we moved to power restrictions and engine mounting methods. Natural evolution once the thread was 'done'.