Sprint turbo

[new to this]

Has any one fitted a turbo to a Sprint engine fitted in a Dolomite ?

[Carledo]

I don't know of anyone who has done this, nor even seen a picture.

I can think of at least a dozen good reasons why it's logistically and practically a bad idea.

But go ahead and prove me wrong if you think you're good enough!

Steve

[new to this]

I don't know of anyone who has done this, nor even seen a picture.

I can think of at least a dozen good reasons why it's logistically and practically a bad idea.

But go ahead and prove me wrong if you think you're good enough!

Steve

just out of interest why is it a bad idea ? Do you know why Triumph fitted the Sprint engine at an angle ?

[Mad Mart]

I was speaking with Jeroen about this the other day. I'm sure he'll be along to enlighten you.

[cliftyhanger]

Has any one fitted a turbo to a Sprint engine fitted in a Dolomite ?

Somebody had put a turbo on a sprint engine, but in a spitfire. Seen some pics. Packaging will always be a challenge.

[Magenta Auto Sprint]

I think it may be a case of cam profiles, I was once told that you need a mild cam for a turbo engine not high lift, Valve overlap etc and blowing through etc.

Malcolm (not sure what I'm talking about before coffee)

[roger440]

I think it may be a case of cam profiles, I was once told that you need a mild cam for a turbo engine not high lift, Valve overlap etc and blowing through etc.

Malcolm (not sure what I'm talking about before coffee)

Id suggest the lack of ability to change profile between intake and exhaust actually works in favour of a turbo. Certainly on stuff ive done in the past, thats worked well. Lack of duration on the intake limits an NA engine, but less so with a turbo.

Im not sure packaging is an issue either. Not near the head at the mo, but on face value turn the exhaust manifold upside down and plonk the turbo in the front corner of the engine bay.

I think the biggest problem is the fact the engine would probably blow up as its not very strong to start with.

[Mad Mart]

But go ahead and prove me wrong if you think you're good enough!

Steve

Come on Steve, that's not like you to be arrogant! I'm sure you didn't mean it that way.

[Carledo]

But go ahead and prove me wrong if you think you're good enough!

Steve

Come on Steve, that's not like you to be arrogant! I'm sure you didn't mean it that way.

Didn't mean to come off as arrogant! I'd kinda like to see it done, just as intelectual engineering interest!

Problems offhand to start with,

The block isn't strong enough, particularly round the centre main web

The crank isn't strong enough (spend enough on tuftriding and stress relief and it MIGHT be)

The conrods aren't really man enough.

The standard compression ratio is too high.

The way the head is secured isn't really up to turbo combustion pressures

Ditto the head gasket.

The cam design doesn't allow for variations in cam timing between inlet and exhaust for max benefit.

Internal engine cooling isn't good enough, a turbo will generate almost twice as much heat as NA.

Packaging IS the big one though. No matter how you slice it, there is no WAY you can get a turbo near enough to the head to avoid massive lag. Roger's simple suggestion of reversing the manifold won't work, the holes don't line up. And in any case the turbo needs to be more or less in the middle or the pulse pathways are all different lengths. So, unless you are willing to have the turbo poking up through the bonnet like some American dragster, it's a bit of a non starter.

The final nail in the coffin is that there are at least a half dozen purpose built turbo'd engines that WILL fit the hole, deliver decent and reliable power increases and cost a lot less (and deliver more) than anything you can do with the Sprint lump. Yes it was cutting edge tech in it's day, but that was 50 years ago, engines have moved on since then!

Steve

[Mad Mart]

I agree with all those points Steve, especially the centre web where the crankshaft bearing caps bolt in.

[GlenM]

Someone on one of the Dolomite Facebook pages is collecting parts to make a T25 manifold for the Sprint engine. I would guess it will have to be a top-mount manifold, with the turbo also positioned quite far forward.

[new to this]

Has any one fitted a turbo to a Sprint engine fitted in a Dolomite ?

Somebody had put a turbo on a sprint engine, but in a spitfire. Seen some pics. Packaging will always be a challenge.

Ive seen a picture of that car,theres a lot more space at the front by the radiator

[new to this]

But go ahead and prove me wrong if you think you're good enough!

Steve

Come on Steve, that's not like you to be arrogant! I'm sure you didn't mean it that way.

Didn't mean to come off as arrogant! I'd kinda like to see it done, just as intelectual engineering interest!

Problems offhand to start with,

The block isn't strong enough, particularly round the centre main web

The crank isn't strong enough (spend enough on tuftriding and stress relief and it MIGHT be)

The conrods aren't really man enough.

The standard compression ratio is too high.

The way the head is secured isn't really up to turbo combustion pressures

Ditto the head gasket.

The cam design doesn't allow for variations in cam timing between inlet and exhaust for max benefit.

Internal engine cooling isn't good enough, a turbo will generate almost twice as much heat as NA.

Packaging IS the big one though. No matter how you slice it, there is no WAY you can get a turbo near enough to the head to avoid massive lag. Roger's simple suggestion of reversing the manifold won't work, the holes don't line up. And in any case the turbo needs to be more or less in the middle or the pulse pathways are all different lengths. So, unless you are willing to have the turbo poking up through the bonnet like some American dragster, it's a bit of a non starter.

The final nail in the coffin is that there are at least a half dozen purpose built turbo'd engines that WILL fit the hole, deliver decent and reliable power increases and cost a lot less (and deliver more) than anything you can do with the Sprint lump. Yes it was cutting edge tech in it's day, but that was 50 years ago, engines have moved on since then!

Steve

thats a lot of negatives for the sprint

[new to this]

I agree with all those points Steve, especially the centre web where the crankshaft bearing caps bolt in.

Would an engine block brace make much difference to strengthening the block in the weak areas

[Carledo]

You'd think I have a downer on the Sprint engine, actually, I don't! For it's day, it was ground breaking and it stayed relatively competitive for at least 10 years. That's a long time by 20th century evolution. Poor build quality did it no favours and the next generations of engines eventually rolled in and surpassed it's clever tech with simpler and more robust designs.

This is how engineering evolves, first examples of anything are simple and crude (and usually not very reliable), the next gen is complicated and a bit better, but still crude. The final gen is simple and clever and most efficient. The Sprint motor is a good example of the 2nd gen tech.

Spend enough money, cherry pick your components, build carefully and you can get a NA Sprint close to 250bhp without it blowing up every 5 minutes. But such an engine would already include a block brace as a matter of necessity. But as close as I can work it out, 250bhp is about as far as this engine will go, stuff that is inherent in it's design won't let you go further. And, TBH, such an engine would be a cammy track monster with a high, narrow power band unsuited to road work. You MIGHT get a more tractable, street usable 250bhp by turbo-ing, (though i'm not holding my breath on that one) but my opinion is that if you got greedy and tried for more, you'd just end up with an expensive pile of broken bits on the road. Whereas the Saab B204 (for example) will go to nearly 400bhp before any bottom end work is needed.

This doesn't upset or bother me, back when I was young and the Sprint was new, there was an engineers maxim for tuning engines and the limit of reliable performance was reckoned to be 100bhp per litre. Most production vehicles of that era struggled to churn out HALF that on a regular basis (American cars of the 80s were even worse, I had a 305cu in (5 litre) V8 Oldsmobile wagon that produced only 140bhp on a good day!) When the YB Sierra Cosworth Turbo came out in the mid 80s, it's 2 litre twin cam was rated at 204 bhp and it was both a revelation and revolutionary, possibly the first PRODUCTION car to actually skirt the limits of the possible.

To a certain extent the maxim still holds true, performance gains per litre have been made by improving peripherals, fuel injection and programmed ignition have helped get the big horses more reliably, as has finer build tolerances (the Sprint's biggest enemy) VVT and turbos have made these power levels available to everyday users. But engines are still made largely from cast steel and the metalurgy is just the same as it was in the 60s and 70s. You do the math!

Steve