supercharging a 200tdi

[flatback90]

jeez boys lets not let this degenerate into a "i'm more qualified/worked on more" type of thread! i was just idly wondering if it was a viable way of getting more grunt sub 1000rpm than the "traditional" ways of vgt,propane,pump fiddling, intercoolers etc. it would be summat different and would make people go "ooh" when they see under the bonnet. however its looking likely that the easiest,most reliable and cost effective way is going to be propane inj. so look forward to silly questions regarding that in the near future. dont stop the discussion though coz it makes for some very interesting reading that i can quote down the pub to shut up the tits in their silly little civics!!!

[cieranc]

Joe, Mini chargers, you mean BMW Mini ones? Thems an Eaton M62 I believe, too small for a TDi.

We had an Eaton M90 on the Sierra (2.9 24v Granada Cossy lump), just the right size, an M112 would have been too big.

[flatback90]

got a feeling jerry thurston said it was the M63? that would suit, or maybe it could have been the sat-nav telling me how to get home......

[Guest otchie1]

I don't wish to interrupt your tennis but 70bhp worth of heat is not 70bhp of useful power, it is just heat. Useful if you had a secondary engine running on steam, but not a lot else. If there was 70bhp of actual thrust coming out of your exhaust the mounting rubbers would be a bit bigger

Yes FF MEng, sorry FF MEng

although I rather like the steam engine idea.....

[Guest noggy]

I don't wish to interrupt your tennis but 70bhp worth of heat is not 70bhp of useful power, it is just heat. Useful if you had a secondary engine running on steam, but not a lot else. If there was 70bhp of actual thrust coming out of your exhaust the mounting rubbers would be a bit bigger

Yes, but it doesnt come out as thrust does it? The energy is wasted as heat in the exhaust gas, nothing to do with thrust fridge.

[Lara]

That's why the vast majority of modern diesels come fitted with a turbo, 'cos it reduces the power of the engine.

From Hillier(p204) adding turbo to CI engine - power increase can be as high as 60%, fuel consumption improved by 10% and exhaust noise reduced.

Note the CI caveat, we're not talking petrol here...

Hillier(p202) "The difficulty of driving a centrifugal blower at very high speeds and the loss of up to 35% of the engine power to provide the drive can be neatly overcome by ..... a turbocharger."

Bell(pV) "...a 200bhp engine dumps aprox 70bhp equivalent of raw heat straight out the tailpipe. That is a tremendous amount of energy that could be put to better use."

McInnes(p11)"Many people think this exhaust-gas energy is not free because the turbine wheel causes back pressure on the engine exhaust system. This is true to a certain extent, but when the exhaust valve first opens, the flow through it is critical. Critical pressure occurs when the cylinder pressure is more than twice the exhaust-manifold pressure. As long as this condition exists, back pressure will not affect flow."

You do realise that it is still more efficient to use an intercooler even on a supercharged engine don't you?

Can we play engineering qualification tennis again now?

You have actually cited your problem my friend,

too many books and not enough experience!!

Experience tells us that exhaust back pressure, even small amounts, does hurt power! Just because you can overcome it with boost does not mean it is not detrimental for power and efficiency! Read books VERY carefully and make sure you understand them fully before repeating.

McInes is a very experienced engineer and I also have his books, however when writing something it is difficult to write a full explanation that is not easily misunderstood by the less knowledgeable without going on and on for reams of explanation.

Lara.

[FridgeFreezer]

Yes FF MEng, sorry FF MEng

I think you mean "FF Dropped-out-of-uni-and-got-a-job-Eng"

Flatback - I really hope you're not actually going to listen to anything Jerry Thurston says, or indeed anyone in the comics. I think they usually bank on the idea that none of their readership would ever bother trying to recreate their strange plans and hence no-one will ever know just how much bodging they do behind the scenes (and in some cases, in full view).

I also heard someone say that the reason there's so many Mini chargers on eBay is they have a defect so an awful lot of them get replaced and the old ones end up on eBay.

[Lara]

Edit. "Got-a-job-Eng" is not only the best quote ever written but the best qualification too!

The amount of idiot "Mr degree race engineers" that come for a job here is amazing and I have even employed a few, 4 in total and all fired within a year! Experience, Experience and intelligence! most important asset imaginable!

Back to Flatback's question though.

A Mechanical supercharger can and will work very well on a small displacement engine, use something like an Eaton from a mini, or a modern Mercedes or Jag blower. We use them regularly and they are great little blowers up to about 1 bar!

A VGT of the correct size will also work, and probably better in the long run, Mine gives boost from 1100rpm onward so little advantage to use a Mech supercharger. however that immediate Snap of power is always fun with a Supercharger (let's call a mech Supercharger a "Supercharger" here)

Gas injection is fine but you will need boost in order for this to work with any noticeable results.

If it is low down power you need (I think it is) you should look up all the good and bad points, add in engineering time and unit cost and then weigh them all together and decide!

However, also throw in the "fun factor" as this is very important

As is the experience gained, even the problem parts as these are what gives you the full understanding of what you read in your books.

And as said before Intercooling should not be under estimated, but not over estimated either!

Lara

[Guest otchie1]

You have actually cited your problem my friend,

too many books and not enough experience!!

Experience tells us that exhaust back pressure, even small amounts, does hurt power! Just because you can overcome it with boost does not mean it is not detrimental for power and efficiency! Read books VERY carefully and make sure you understand them fully before repeating.

McInes is a very experienced engineer and I also have his books, however when writing something it is difficult to write a full explanation that is not easily misunderstood by the less knowledgeable without going on and on for reams of explanation.

Lara.

Lordy Lordy how rude you are. Does your experience tell you why a carefully tuned exhaust allows an engine to generate more power than one in which the exhaust port just vents to the atmosphere? Explain that away Mr back-pressure-is-always-bad.

All engineering is a compromise; in this case between increased back pressure at low rpm and the huge boost in power that a turbo brings.

Your experience, like that of so many 'experts' is built using machines designed and built by engineers who spent years studying exactly how things work and then figuring out how to make them better. Higher education is all about understanding rather than copying or memorising large chunks of stuff. A design engineer will apply his knowledge of thermodynamics and fluid mechanics and offer a solution which will be tested for 'buildability' by materials engineers and finally tested by mechanical engineers. After all that and a few millions of $$$ they will reach the best compromise for the product. It won't be the most efficient turbo but it will be a viable solution. And then you come along and think you can improve it with your 'experience'.

Can I design a novel and better turbo vane? No. Can you? Hell no.

That said, the solution is likely to be in variable exhaust flow - at low rpm route the gas via a non-turbo route and use a direct drive super-charger to give boost, then at higher rpm, switch the exhaust route so that the turbo spins up. Probably best to have a bit of overlap to avoid lag. Maybe use the residual supercharger spin to spool up the turbo.

If you look hard enough I'm sure someone has already designed it, if not. consider this to be a patent application

As it happens, my qualifications start with engineering C&G and go up via BTEC and on with lots of commercial dirty spanner spinning thrown in. I had to pay for by degrees somehow

[muddy]

OR you could fit a more suitable engine in the first place? N/A V8 maybe?

Excellent thread mind you

Will (Bigger-hammerEng)

[FridgeFreezer]

It's a fair point, the money spent tweaking a TDi can buy a V8 (or indeed another engine altogether) that will give similar results out of the box. However, I do like seeing people try something different (even if it is a diseasal) so I reckon it's worth a pop.

[pat_pending]

Surely the point of the exercise is to achieve a cost effective, easily engineered solution to a requirement, in this case for more power.

Not to spend more effort/money than is necessary, to show what a clever b*stard you are.

Of course it's possible to supercharge this engine, but it's already set up for a turbo, suitable VGTs are available, others have gone this route... and it works. IMO the re engineering required to fit one would be considerably less than the supercharger route.

If we realy want to rattle this one out, lets see some costings for both types of installation, and the potential gains for each.

[FridgeFreezer]

Surely the point of the exercise is to achieve a cost effective, easily engineered solution to a requirement, in this case for more power.

There's also the fact that very few people have done it, and yet everyone's saying you shouldn't. Reminds me of when I built my truck hence I say f**k it, go for it, if it doesn't work at least you've proved it one way or another.

[Lara]

Hi Mr Otchie,

You seem to want to get into a pissing fight! I am not very interested,

Mr McInnes qualifications do not transpose to those who read his books!

You have evidently not read them well enough or allowed yourself time to fully understand what he is saying, or what I was saying for that matter! Easily done and I have also been guilty of this. or maybe you just responded a little rashly?

McInnes quote you added says very clearly that in his opinion if the exhaust outlet pressure at the valve is twice that of the manifold, then exhaust back-pressure has very little effect, quite possibly true! but think for how long this "Critical pressure" goes on for.

Experience experiment.

Many years ago, I was doing development of a 1.4 litre 8 valve turbo engine, this engine was production based NA engine, Turboed and modified by me, and was giving 296bhp @ 6800 rpm, @ 2.2bar boost. I made a fixture out of a Yamaha FZ750 engine and transmission brake to power a separate turbo to test exactly what we are discussing.

When hooked up (and this was no mean feat I can tell you) to run next to, and boost the other engine on the dyno we got 316bhp at the same revs with 2bar boost as this was all we could achieve from the Yam engine. Now where did that extra power come from? I think I was right in presuming it was mostly due to back-pressure and driving the Turbo! You won't read that in a book though.

You read that back-pressure tuning is good for power, Semi true, but what you are actually doing is "pressure wave tuning" and although back-pressure is one of the ingredients, it is not the trigger for power, it is an unavoidable sufferance, the pressure wave if tuned correctly will actually "Suck" at the valve area as in "Negative pressure" not back-pressure, you may also believe the advertising blurb in the "super trap" adverts, Testing shows this to be absolute bull, and they do not tune any power except all of it down!! Back-pressure on it's own is bad for power! Unless driving a Turbo or exploited in other ways.

My experience is gained in Engine design, From scratch in some instances! From race car preparation, From running a race team of 6 cars, 3 of them supercharged, 4 of them on alcohol, and One with rather a few fuel additives, From playing and experimenting all of my life and now From running / owning one of the Europe's top restoration / historic race preparation companies, My Landy engine if that is what you were referring to is just a little toy on the side! Again I am not having a pissing match, but don't think that you are the only person on here with a few qualifications, I too went to college etc (luckily I was company sponsored) and my BTEC is in the bin where it belongs (honestly!)

You only understand something truly when you have "done it your self" No other way in my experience!

There are many more experienced people on here I am sure who can laugh at yours and my experience put together and P quite happily on us both, so no point into pissing in the wind!

Let us answer the question asked!

Flatback,

This is a picture of a blower that I personally designed and built for one of our race cars, it was done to improve efficiency of the original blower in order to reduce the speed at which we needed to drive it, The engine was 1.5 litres and gave 260bhp,

So blowers can work on small engines! don't be put off, just try it and have fun!

Lara

[Daan]

If you want to go really groovy, why not have both, the blower at low rpm, and the turbo takes over for higher rpm while the blower disengages, merc CLK stylee.

Daan (i can lose some weight here ENG).

[flatback90]

oooh supercharger porn......thanks for that lara dont think i have the expertise to make one from scratch though! maybe bolting one on would be do-able.....think i'm gonna go get the tdi in the yard that has no turbo and throw it up on the bench for a look see although i think a 300 might be better for mounting the blower on the existing aircon mounts. first i'm gonna finish the trayback for the 3peaks and get my quad sorted for winter

[bishbosh]

Nah,

What you need is [irn Bru accent on] girders[/irn Bru]

Bish [Chartered Bridge Engineer]

Well I had to get my discipline in here somehow!! All this talk of pressure waves and other such gobbledy gook... tsk tsk

[FridgeFreezer]

You could go for a small centrifugal one like this:

http://www.extraefi.co.uk/cobra/Page31.htm

I think someone in our club had one a while back cheap off eBlag, god knows what it was off though.

[Lara]

You can get the Paxtons in the states, they are a re-design of the old pre-war Paxton design with a much improved gear drive to the compressor shaft, They are very expensive to buy new though! not sure how good compared to others though as never used a modern one! Although AMG and Brabbus used them quite successfully on some of their bigger engines!

Flatbed,

If you are going to the Three Peaks, look me up and we can chat, I will be in the "Dirty Buckers and Belgian Bennys" team, Will get there on Friday evening. Staying at the Hi-B. Is this your first time at the TP's?

Lara

Steam-Eng

P.S.

I have quite a few blowers of various types on the shelf if you need one.

[Aragorn]

You could always, you know, use a lower gear and raise the RPM's a bit....

I've never understood why people with diseasels focus on a tiny band of RPM from about 1200rpm to 2000rpm. POWER is the measure of how much work the engine is doing, and thats available all the way to the governor.

[Guest noggy]

Otchie... ive got no qualifications, but spend a hell of a lot of time reading and playing in the workshop. Experience and testing is much the better way if educating yourself!

Not saying i know more than you, but i have a better understanding of exhaust dynamics than you!

[RPR]

I am completely unqualified. The solution adopted by much of the diesel racing and pulling crowd in the US (these are however diesels on the 5.9 - 7.5 ltr scale) is generally: twin turbos, propane injection, water injection (cooling). While I am not qualified, these are the solutions that seem to have proven most successful with those who are. Worth looking at.

[Lara]

I am completely unqualified. The solution adopted by much of the diesel racing and pulling crowd in the US (these are however diesels on the 5.9 - 7.5 ltr scale) is generally: twin turbos, propane injection, water injection (cooling). While I am not qualified, these are the solutions that seem to have proven most successful with those who are. Worth looking at.

Absolutely agree that any and all of these things work very well but you do need to wind your engine up rather a lot to get the most out of them, and they all rely on boost pressure being present, and most are aimed at "Max output"

I think what Flatbed wanted was the fastest transition between off and on boost, I think that for this it would have to be a Mechanical Supercharger, or Nitrous Oxide injection, or a quite special turbo. (or two) there are drawbacks with all three but probably less with the first in my opinion. (and mine is no more valid than yours, it's just mine )

Lara

[plasticbadger]

i thought about doing this,

i was going to have the super charger blowing through the turbo and use an electro clutch on the super charger to control when it comes on, basically when the turbo is at full boost you dont need the super charger running as the point is to reduce lag etc not get lots more boost, this could be controlled quite easily with a pressure switch controlling the clutch, the only thing with this system is you need some sort of change over flap so the turbo doesnt have to suck through the supercharger when the supercharger isnt running, its nothing special or complicated but would just need a bit of thought.

also the fuel pump wont need any adjusting as it is already sensing the boost pressure and fuels the engine accordingly, all you are doing is getting more boost earlier (not waiting for the turbo) which means it will deliver more fuel therefore more power sooner.

i was all set to do this to mine but i happened to stumble across a vnt turbo so i am going down that route instead,

i will be very interetsted to see how you get on

Nobody seems to be keen about this, but I guess in your job you have been swayed by the Volvo D4 and D6 marine engine. For others who don't know them so well the D4 and D6 use a turbo, supercharger and aftercooler (water to air charge cooler) to produce (on the D4) 300hp from 3.7L. The impressive bit though is the torque that stays above 600Nm from 1500 to 3500 rpm (max is 700Nm).

I've never seen a VNT / VGT turbo engine produce as flat a torque as the D4 and never felt one pull so well from the bottom end. Some versions are pretty good including Volvo's own D3 marine / D5 automotive engine. The combination of the turbo and supercharger is the closest I ever experienced to a big capacity petrol engine.

Once you figure out how to to manage the change over between turbo and supercharger and what to do with the air and fuel management the rest is easy

I seem to remember there was a pretty good explaination and schematic in one of those books mentioned, which I'll look up. I think it was of the Lancia Delta S4 Super/Turbo set up, which did use two intakes so that the turbo wasn't sucking through the blower. It would be a very interesting project!

[Lara]

To be honest although probably not ideal, pulling through a disconnected free turning supercharger would work quite well, If the supercharger drive fails the engine usually runs in normally aspirated form quite satisfactorily if nothing causes the blower to foul, so if engineered well, just disconnecting it with a clutch should work OK, (not ideal but probably very satisfactorily I would think) This would be very worth while experimenting with.

Lara.