Daydream - building a 1.5L CR engine.

Jetmugg said:

If I were to import a 3 cyl TDI from Europe, what else would I need (wiring harness, ECM)? I'll assume for the time being that the 3 cyls will bolt up to the commonly available transmissions in the US. Unless someone tells me otherwise.

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In theory, you'll just need the engine wiring harness. It should work with locally available EDC15 with the correct file.

Tranny will bolt up, the only thing is you'd have to use a G60 flywheel balanced correctly in a machine shop. The stock flywheel is somewhat smaller (218mm?) and is balanced weirdly to compensate for the off-beat motor.



Ash

TDIMeister said:

Fast, cheap and practical. Pick two.

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What if one were to mount dual injection pumps turning at half speed? (Bigger sprocket) You could get twice the injection pulses per revolution of the pump (by pairing injector lines) while allowing the pumps to turn at half the speed of the cam.

Then you can find a way to balance a short-stroke crank capable of 10,000rpm and your only challenge is the "minor" detail of re-working the head to take 10,000rpm.

Why would you want to do that? The common-rail system has no need of "injection pulses", the "injector pump" is just a pressure pump. If you use a "pumpe-duse" 1.4 TDI, then each cylinder has its own tiny pump and nozzle, it's exactly the same as on the 4-cylinder engines. There is no distributor-pump version of a 3-cylinder TDI.

You're not going to get a diesel combustion system to operate at 10,000 rpm in an engine of this scale, anyway.

I think the approach that makes sense is to just start with a production 1.4 TDI (be it common-rail or pumpe-duse), keep it in the same RPM range as stock (up to 5000 rpm or thereabouts), and hot-rod it traditionally - different turbo or possibly series turbo. For the application that the original poster has in mind - a top-speed test - it isn't necessary for the engine to make good power right off the bottom - it just needs big top end power. Low pressure outer turbo, high pressure inner turbo, size them both for best operation at 4000 - 4500 engine RPM, the heck with what it does off-design (lower engine RPM - so no need for flapper valves to sequence the turbochargers or bypass them), big injectors, big intercooling.

Sorry, I was not being clear!

I was thinking of using two VE pumps on an ALH type block de-stroked to 1.5. Like a fast turbocharged Japanese motorcycle screaming-4 cylinder engine... only it's a Frankenstien diesel screamer.

Nothing wrong with common rail either, but I guess I have been assuming that the common rail pumps have a maximum speed that is similar to the old VE pumps. Can you slow the CR pump speed vs. the engine? I thought maybe there were pump pulses that would benefit the rail pressure when injection was supposed to occur?

How much distance is this top speed going to be measured over? 1.4 TDI + R783 + 1756VK = 160+ WHP. In theory anyway. I've been meaning to do such a build, but don't see it happening till next year.

Ash

manual_tranny said:

Sorry, I was not being clear!

I was thinking of using two VE pumps on an ALH type block de-stroked to 1.5. Like a fast turbocharged Japanese motorcycle screaming-4 cylinder engine... only it's a Frankenstien diesel screamer.

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On a 4-cyl each injector pump is producing a pulse every 180 degrees of crank rotation (and it's distributed between 4 injectors). Run it at half speed and it's only producing a pulse every 360 degrees. But there is still a cylinder demanding fuel every 180 degrees. Don't see how this is going to work. Even so, the VE pump will deliver fuel up to the rev limit of the engine anyway, and you are going to get into combustion problems at very high revs.

VW Motorsport was making 240+ horsepower (that they admitted to) out of a 4-cyl distributor-pump TDI years and years ago, and that was with a single injector pump, plenty of boost, plenty of injector nozzle, plenty of intercooling, and it was in the 3500 - 4500 engine rpm range ... This path has been gone down many times before and I don't see the need for re-inventing the (obsolete) wheel.

And still, if you are going to make a hot-rodded TDI with a 1.5 litre displacement limit, just start with a stock engine within the displacement limit (3 cylinder 1.4 pumpe-duse or common-rail), do all the same sorts of things to it, and avoid re-inventing the wheel. The thing that the original poster seeks to do, need not involve re-inventing anything.

manual_tranny said:

Nothing wrong with common rail either, but I guess I have been assuming that the common rail pumps have a maximum speed that is similar to the old VE pumps. Can you slow the CR pump speed vs. the engine? I thought maybe there were pump pulses that would benefit the rail pressure when injection was supposed to occur?

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The common-rail pump RPM isn't the limiting factor. The combustion system (the concept of compression ignition of fuel injected late in the compression stroke, i.e. any diesel) and specifically the mixing time of air and fuel and the ignition delay of the fuel, is the limiting factor.

The common-rail pumps do produce pulses of fuel that are intended to be more-or-less synchronized with demands from the engine. You want the common-rail pump delivering fuel somewhat before each piston in the engine reaches TDC and keep delivering it for some time after TDC. Then there is a dead spot in which there is no need for it to deliver anything because there is no cylinder demanding fuel, so they don't.

GoFaster said:

The combustion system (the concept of compression ignition of fuel injected late in the compression stroke, i.e. any diesel) and specifically the mixing time of air and fuel and the ignition delay of the fuel, is the limiting factor.

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Yup.

GoFaster said:

On a 4-cyl each injector pump is producing a pulse every 180 degrees of crank rotation (and it's distributed between 4 injectors). Run it at half speed and it's only producing a pulse every 360 degrees. But there is still a cylinder demanding fuel every 180 degrees. Don't see how this is going to work. Even so, the VE pump will deliver fuel up to the rev limit of the engine anyway, and you are going to get into combustion problems at very high revs.

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Yes, I still haven't explained what I was thinking properly.

The reason for two pumps is that each pump could fuel just two cylinders, allowing them to turn more slowly relative to the crank speed. The VE pump doesn't fuel very well at high rpms, which is why I postulated that two pumps might be able to supply an engine that turned faster.

GoFaster said:

And still, if you are going to make a hot-rodded TDI with a 1.5 litre displacement limit, just start with a stock engine within the displacement limit (3 cylinder 1.4 pumpe-duse or common-rail), do all the same sorts of things to it, and avoid re-inventing the wheel. The thing that the original poster seeks to do, need not involve re-inventing anything.

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I suppose my advice isn't any good for the OP, but as usual I'm just throwing wacky ideas out there to see if they might have merit.

Matt-98AHU said:

You're not technically wrong, but short strokes don't make so much sense with diesels. It's very limited by how fast the fuel can burn, even full on diesel-powered Le Mans race engines don't exceed 6000 RPM AND they've already passed their horsepower peak by that point.

A longer stroke makes sense to allow proper time for a complete burn of diesel fuel plus it has a leverage advantage for more torque. With a diesel, a big bore short stroke setup really isn't going to gain you much, IMO.

Makes GREAT sense for gas racing engines, however. Oversquare engines are the name of the game in Formula 1 where, before regulations imposed a mandated rev limiter at 18,000 RPM, they were capable of more than 20,000 RPM! Not very high torque engines, but since they revved so high and were able to produce enough torque at those RPMs, the horsepower figures are quite impressive. Plus you just shorten the gearing so you get more torque multiplication to the wheels and you have a recipe for manic acceleration.

My vote is on a European-sourced 3 cylinder.

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The bore and stroke do not effect the time available to combust - only RPM's and injection timing.

You obviously need to stay within practical RPM limitations for diesel combustion and whatever fuel delivery mechanism is chosen. For the same displacement and rod ratio a longer stroke won't make any more torque on average.

The larger bore you have the more room that is available to get air in/out of the cylinder efficiently.

A lower rod ratio might be slightly beneficial for higher RPM diesel combustion as the piston moves away from TDC faster for a given RPM thus maybe allowing more injection advance for the same peak cylinder pressure?

I think importing a PD or CR 3 cylinder is easiest. I think a de-stroked CR 4 cylinder would deliver the most performance

Fix_Until_Broke said:

The bore and stroke do not effect the time available to combust - only RPM's and injection timing.

You obviously need to stay within practical RPM limitations for diesel combustion and whatever fuel delivery mechanism is chosen. For the same displacement and rod ratio a longer stroke won't make any more torque on average.

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While this is all true, the fact that there is essentially an upper boundary of 5000 - 6000 rpm on a diesel engine pretty much imposes a "minimum stroke" if you want to have an efficient engine.

It has to do with the mean piston speed. Gasoline engines typically have mean piston speed at redline in the 20 m/s range. The upper boundary (Formula 1 car engines, etc) is in the 26 - 28 m/s range. Diesel engines are typically a bit lower than 20 m/s at redline. For example, VW TDI with 95.5 mm stroke and 4700 rpm redline is at 15 m/s.

If you are fixed with an upper RPM boundary in that range then sure, you COULD use a shorter stroke and lower-than-necessary piston speed, but for a given displacement it results in a wider bore with more distance required for flame travel (possibly combustion problems) and it adds more area to the combustion chamber for heat loss for a given displacement (loss of efficiency), and more piston ring sealing surface (tendency towards higher leakdown). Since the forces on pistons, con-rods, and cranks is dependent on the piston area, then for a given engine displacement, a wider bore and shorter-than-necessary stroke requires heavier pistons, heavier rods, heavier engine.

Strictly speaking, one could use a stroke even longer than 95.5mm for a 4-cyl diesel engine in the 2.0 litre range while remaining in the target engine RPM and piston speed range, in the interest of making the bores narrower, but this would force the engine to be taller, resulting in hood clearance problems.

I'm not sure if there's a disadvantage to a "lower-than-necessary piston speed", is there a "necessary" piston speed? The piston speed is pretty low at idle or lower RPM's and there does not seem to be a problem there? Maybe I'm missing the point?

Given that diesel combustion is relatively spontaneous (unlike gasoline combustion which originates from one spot) I wouldn't think that the wider bore (same as a 1.9) would be a problem.

Heat loss I agree with, but I don't know why the forces would be any different on the pistions/rods/crank/ or why it would require heavier pistons or would have any more blowby compared to a 1.9?

It's not that a low piston speed won't work. It's just that the higher surface area exposed to combustion conditions will lead to higher heat losses and lower thermal efficiency, and the higher surface area will lead to the pistons, rods, crank, etc all having to withstand more force. Bottom line, the engine will be heavier and less efficient than if it were designed with a longer stroke i.e. higher piston speed.

The forces on the pistons are higher for the simple reason that with a shorter stroke, the bore has to be bigger for a given displacement, and for a given cylinder pressure, that means more force!

Agreed on all counts if designing from scratch, but de-stroking a 1.9 should address most (if not all) of those concerns. The pistons/rods/rings etc don't know that the crank is shorter.

Could you simple just build a big 1.5L IDI turbo? Why would this not work? modify 1.5L rotating assembly to lower CR to 18-19:1 slap a k03 and a gt2871 on it and go (just grabbed 2 readily available turbos off my head) large front mount and go.

K.I.T.T. said:

How much distance is this top speed going to be measured over? 1.4 TDI + R783 + 1756VK = 160+ WHP. In theory anyway. I've been meaning to do such a build, but don't see it happening till next year.

Ash

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OR with a GTB2056vk and Firad injectors + ported head 200hp++ and 150mph with good gearing and aero.

a full 1.4TDi setup would be around £2k shipped + modifications obviously

K.I.T.T. said:

How much distance is this top speed going to be measured over? 1.4 TDI + R783 + 1756VK = 160+ WHP. In theory anyway. I've been meaning to do such a build, but don't see it happening till next year.

Ash

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At Bonneville, the "ShortCourse" is 3 miles. You start from a dead stop, accellerate for the first 2 miles, then the official timing is performed between mile 2 and 3. The short course is used for attempts up to 175 mph. Over that, and you go to the long course, which is 5 miles.

I'm no TDI expert, but do know a bit about Mercedes diesels (IDI) and what guys do to them to get big power. It's all about fueling and airflow, while keeping the intake charge and EGT temps in a safe range. For a land speed attempt, the engine rpm isn't super-critical. Every attempt is made to match the peak power rpm approximately to the speed that you are trying to run, through a combination of gearing and tire size.

So if the engine makes peak power at 5,000 rpm, you try to make sure that the engine can "get there" before the aerodynamic drag prevents any additional rpms.

SteveM.

v8 coupe said:

Could you simple just build a big 1.5L IDI turbo? Why would this not work? modify 1.5L rotating assembly to lower CR to 18-19:1 slap a k03 and a gt2871 on it and go (just grabbed 2 readily available turbos off my head) large front mount and go.

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That's the most straightforward, traditional approach. Using "off the shelf" VW parts, the 1.6 turbo block has a few advantages (head bolt size, oil squirters for the pistons, a beefier casting), and the 1.5L rotating assembly should be a direct bolt-in.

This is a great discussion, I'm just trying to figure out if there is a better way to go, by way of TDI technology, as compared to the older IDI stuff.

Jetmugg said:

That's the most straightforward, traditional approach. Using "off the shelf" VW parts, the 1.6 turbo block has a few advantages (head bolt size, oil squirters for the pistons, a beefier casting), and the 1.5L rotating assembly should be a direct bolt-in.

This is a great discussion, I'm just trying to figure out if there is a better way to go, by way of TDI technology, as compared to the older IDI stuff.

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what about a ahu head on 1.5L bottom end in 1.6L block? you can always add the squirters and larger head bolts to the 1.5L.

I'm eager to learn more about the possibility of an AHU head on a 1.5 or 1.6 block. I don't know enough about the TDI series of engines to know if it's possible. Is the AHU a direct injection engine?

Where would you plan to obtain 76.5mm TDI pistons?

The tops of the IDI pistons are completely different from the TDI ones and not in the slightest bit interchangeable.

That's what I thought. The IDI and TDI heads and pistons are not compatible. That seems to negate the suggested possibility of an AHU head on an IDI block.

Take a stock ALH, leave #4 piston, rod, and followers out, leave all the guts of the injector out so its just bypassing the fuel back into the return lines... bingo, less than 1.5L engine... and it'll bolt right in any place the ALH did. You may have to do some ECU tweaks.

Lol

oilhammer said:

Take a stock ALH, leave #4 piston, rod, and followers out, leave all the guts of the injector out so its just bypassing the fuel back into the return lines... bingo, less than 1.5L engine... and it'll bolt right in any place the ALH did. You may have to do some ECU tweaks.

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"-Hey man what's that lumpy idle?

-O, that's just a high performance mode, you know, where you run a 3 cylinder motor in a modified 4 cylinder block."

^ OilHammer... I think I did this once, but I left the injector and rotating assembly (for the most part) in place. I just knocked the exhaust valve out and put half the piston through the exhaust.... Ran pretty well too.....

Soooo. 56 posts later and still the realisation that modding a 3 pot isn't the easiest way forward?


http://www.ebay.co.uk/itm/SKODA-FAB...CarParts_SM&hash=item3a6b6e848e#ht_500wt_1361
get bits from this car and you can boast your engine was assembled in a former Soviet bloc country (I've watched them assemble these 3 pots in the flesh on a tour of the Skoda factory in Mlada Boleslav )


http://www.ebay.co.uk/itm/2007-SEAT...arts_Vehicles_CarParts_SM&hash=item336dc98e60
or this one if the idea of a prancing Spanish horse is more your style


http://www.ebay.co.uk/itm/VW-POLO-A...arts_Vehicles_CarParts_SM&hash=item1c1c122002
or just solid quality from Zee Germanz

Keebler145 said:

"-Hey man what's that lumpy idle?

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Actually, it probably would not be any lumpier than a 3 cylinder already is, given the extra mass and compression of that piston would be gone.

Incorrect. It will be much rougher than an as-designed 3-pot.

Easiest way forward is to start with a 1.9 TDI of your choice, a crankshaft de-stroked by 20mm, custom rods 20mm longer, fuel system already known to give X HP in the original 1.9 L displacement, sufficient boost to clear the smoke. Done.