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TDI Engines...
HMSMotorsport - 10/7/12 at 01:46 PM

Following on from my questions about Duratec's, someone suggested a TDI engine with a remap. I've not noticed this being done before so is there a fundamental reason that this wouldn't work? The car in question is a Tiger Avon.

The idea would be either a Ford TDCI or VAG Diesel engine....

loggyboy - 10/7/12 at 01:48 PM

Diesels are smelly and noisy, but also give loads of torque, not something thats really needed fot a sub 700kg car.

HMSMotorsport - 10/7/12 at 01:50 PM

That's true but this is solely a race car. Doesn't have to look or sound pretty, it needs to be fast and reliable.

roadrunner - 10/7/12 at 02:09 PM

If you went down the diesel route, you would need a very low geared diff.

Irony - 10/7/12 at 02:57 PM

I own a GT TDI PD 150 Golf and I am constantly impressed with the engines performance and economical running costs. It'll sit at 90 on the motorway and return 48mpg. If you sit at 50mph it'll return 72mpg but thats boring. Not many normal cars will out do it between 40-60mph.

Not sure about racing one in a Seven - a - like though. I do know that if you boot it a huge cloud of blackness comes from the exhaust restricting everyone behind you vision and respiration1

D Beddows - 10/7/12 at 03:29 PM

The electricery involved puts most people off once they look more into it. I've got a company 08 plate Golf TDI and I do actually like the engine..........in a company car

HMSMotorsport - 10/7/12 at 03:31 PM

quote:
Originally posted by Irony
I own a GT TDI PD 150 Golf and I am constantly impressed with the engines performance and economical running costs. It'll sit at 90 on the motorway and return 48mpg. If you sit at 50mph it'll return 72mpg but thats boring. Not many normal cars will out do it between 40-60mph.

Not sure about racing one in a Seven - a - like though. I do know that if you boot it a huge cloud of blackness comes from the exhaust restricting everyone behind you vision and respiration1


Yea my dad's got a Skoda Fabia VRS which Forge Motorsport extracted 200bhp out of. When he was drunk at Le Mans he finally admitted its quicker than his Porsche Boxster S! We had a spirited run through some country lanes a while back and I could only catch him when he eased off a little to 'keep it above 45mpg'.

quote:
Originally posted by D Beddows
The electricery involved puts most people off once they look more into it. I've got a company 08 plate Golf TDI and I do actually like the engine..........in a company car


Doesn't worry me too much, plenty of expert friends when it comes to electrical work. I can build an engine but I wouldn't wire up a headunit, therefore I am more than happy for someone else to have the headaches of wiring the damn thing!



[Edited on 10/7/12 by HMSMotorsport]

scootz - 10/7/12 at 03:46 PM

Is a diesel engine not typically heavier than an equivalent petrol one?

D Beddows - 10/7/12 at 03:57 PM

I genuinely wish you the best with it - people are often starting topics like this and no one can ever give a proper answer because so few people have done it! (modern TDI's that is not ancient Ford/Izusu diesels )

MikeRJ - 10/7/12 at 05:17 PM

A compact RWD gearbox is likely to be a problem - ye olde Type 9 would spit it's guts out pretty quickly with a modern turbo diesel behind it.

Besides the practicalities, a diesel engines in a sports car is a travesty. Listening to daga daga daga and spewing black smoke in a 7 is surely a good reason to avoid (and even the very best 4 pot diesels still sound like diesels, no matter what various owners might try to say).

zilspeed - 10/7/12 at 05:20 PM

Diesels have a power band which is so narrow it makes the one on a bike engine look lovely and flat.

That's why there are so many 6-7-8 speed transmissions these days. to keep it in the sweet spot.

Don't get me wrong, when you're in the sweet spot, the torque is mega, but the transmission is everything to keep it there.

My own daily driver is a Passat TDI with 6 speed DSG.
As a thing for crossing ground effortlessly, it's fantastic.
It's very easy to stay in the zone where the engine is somewhere between 1500 and 2500rpm and the box does all the works.

A Locost or it's like isn't about bowling along like that though with the engine kept in it's happy zone.

A decent bike engined car with say a Hayabusa and suitable diff with it's comparatively wide power band will pull nigh on 60mph in first gear froma standing start.
A diesel must be in the right rev range and the turbo must also be in the zone for it make the torque that we all love them for.
Then there's the elastic nature of the power delivery.
In my Passat, I love the shove as the torque comes in.

I don't love the inevitable delay whilst I wait on full boost.
A bike engined car in comparison has lightning fast throttle response.

If you want a tiny little sports car that nervously responds to your every thought, a diesel isn't the right choice of engine.
If you want to waft along on a big fat pillow of grunt, by all means go diesel, otherwise, a petrol engine with whipcrack throttle repsonse is infinitely more suited to the chassis.

I can imagine nothing worse than a type 9 with it's horrid gear ratios bolted up to the back of a diesel and completely failing to keep it in the rev band it needs to be in.
Bike engines have 6 close ratios for a good reason, so do modern diesels.

rodgling - 10/7/12 at 05:21 PM

The E36 BMW gearboxes will take a fair bit of torque (the 5 speeds are the ones to go for, being both stronger and lighter) - an M3 will put out 260 lb feet so that should be fine for this application?

Steve Hignett - 10/7/12 at 05:23 PM

My current car is a year 2001 VW Golf GT TDi 130 and is chipped to 170/180 ish and I reckon that it's quicker than my last golf (Year 2000 V6 4Motion) !!!

roadrunner - 10/7/12 at 08:25 PM

Diesels only feel fast, because of the turbo shove, an equivalent powered petrol, might feel flat, but will keep up with diesel due to the way power is delivered across the rev range.

loggyboy - 10/7/12 at 08:32 PM

quote:
Originally posted by roadrunner
Diesels only feel fast, because of the turbo shove, an equivalent powered petrol, might feel flat, but will keep up with diesel due to the way power is delivered across the rev range.


But its rarely possible to compare, as generally TDs have massive amounts of torque compared to power, but generally petrols have similar figures, so if you take a 150bhp diesel it will woop a 150bhp car as the diesel would likely have 250+ft/lbs. Also generally ive found that the diesels dont have much shove as the turbos arent huge and kick in faily low down, and prior to kicking in they have virtually nothing.

JoelP - 10/7/12 at 08:42 PM

quote:
Originally posted by loggyboy
quote:
Originally posted by roadrunner
Diesels only feel fast, because of the turbo shove, an equivalent powered petrol, might feel flat, but will keep up with diesel due to the way power is delivered across the rev range.


But its rarely possible to compare, as generally TDs have massive amounts of torque compared to power, but generally petrols have similar figures, so if you take a 150bhp diesel it will woop a 150bhp car as the diesel would likely have 250+ft/lbs. Also generally ive found that the diesels dont have much shove as the turbos arent huge and kick in faily low down, and prior to kicking in they have virtually nothing.


I dont buy the argument myself. Torque is linked to power by an equation, the diesels only have more torque because they produce the power at a lower revs. The petrol engine, being at a higher rev, can use the gearing to multiply the torque AT THE WHEEL back to equivilent. The lurching power of a modern diesel is just the turbo spinning up hard.

My audi 2..7t doesnt have the boost feeling because it has a second turbo filling the gap at the bottom, so whilst it doesnt give you the stomach turn of a car with a single turbo, its actually pretty damned fast.

sdh2903 - 10/7/12 at 08:42 PM

Rather than the hassle of making a fwd motor work. What about a 320d engine and box. I'm currently driving one and can't fault it. A remap is on the cards for 180 bhp in the near future. not sure how wide the box is though.

Valtra - 14/7/12 at 10:41 AM

quote:
Originally posted by sdh2903
Rather than the hassle of making a fwd motor work. What about a 320d engine and box. I'm currently driving one and can't fault it. A remap is on the cards for 180 bhp in the near future. not sure how wide the box is though.



Have to agree this is by far the best route but you will need the rear axle as well or similar (perhaps lower) gearing . It is really all about the gearing with a diesel due to the relatively slow revs and narrow power band . the only downside for racing would be off the start line where super high gearing and narrow power band always hamper a manual derv as it gets into it's stride . Weight could be an issue of course but there are plenty of fellas here dragging pintos about , and I would think the difference is marginal mainly down the the extra pipework , turbo, intercooler, pump etc . This could be partly offset by less fuel carried and/or less stops on an endurance event.

As for the feel of a derv , it is different but not always inferior , good modern units have crisp response to the pedal which mimics true throttle response of a petrol, to give a keen and eager feeling. VAG and BMW will be the best .

Nobody has mentioned the Sierra Diesel....probably with good reason. but the diff could be useful

Steve Hignett - 14/7/12 at 11:13 AM

quote:
Originally posted by Valtra
Nobody has mentioned the Sierra Diesel....probably with good reason. but the diff could be useful


The diff may be "useful" as you put it, due to the taller gearing, but because of the multitude of ZX10R and Turbo Blades/R1's the 3.21's are pretty scarce now, and often command a premiun (rightly or wrongly).

It's probably worth looking at the donor car for the Diff aswell, assuming it is of a suitable size/weight...

bi22le - 14/7/12 at 11:30 AM

Will your proposed race class allow diesel?

Many Dont.

MikeRJ - 14/7/12 at 11:56 AM

quote:
Originally posted by loggyboy
quote:
Originally posted by roadrunner
Diesels only feel fast, because of the turbo shove, an equivalent powered petrol, might feel flat, but will keep up with diesel due to the way power is delivered across the rev range.


But its rarely possible to compare, as generally TDs have massive amounts of torque compared to power, but generally petrols have similar figures, so if you take a 150bhp diesel it will woop a 150bhp car as the diesel would likely have 250+ft/lbs. Also generally ive found that the diesels dont have much shove as the turbos arent huge and kick in faily low down, and prior to kicking in they have virtually nothing.


This is one of the most commonly held fallacies with diesels. The thing that propels the car is the torque at the wheels, not the torque at the flywheel. Given 150bhp, whether produced from a diesel or a petrol the same torque can be applied to the wheels with suitable gearing. The diesel engine will produce the 150bhp using more torque and low RPM, so the gearing has to be higher than the petrol engine which negates the torque advantage at the wheels.

Diesels feel much faster than they are because of the very non-linear torque delivery from the engine.