2.5s closed deck (impressive triumph)

[stingray]

All I see is an old used 2021 piece for sale. Nothing special here.

 

[Kevin frazier]

Most wont know what there looking at, but there’s probably not an engine builder on the planet that would choose open deck sleeves compared to the closed deck design. You sure wont see any open deck designs in nhra.

 

[SpazOnaR3]

Most wont know what there looking at, but there’s probably not an engine builder on the planet that would choose open deck sleeves compared to the closed deck design. You sure wont see any open deck designs in nhra.

While I'm a fan of using extremes to test the bounds of an idea, sometimes we get a little apples-to-oranges. In my experience with stuff like this, I've started looking more at specific output and intended purpose for things, rather than what may be the 'pinnacle' of design or and idea.

A 2.5L engine making 500hp is impressive; call it 200hp per liter. While that number on a street going vehicle would pop eyeballs 50 years ago (turbos be ****ed), that is well within the design envelope for a lot of open deck engines. Comparing anything to an NHRA Top Fuel engine is lunacy... those engines are making over 1200hp/liter on a conservative estimate (some would say 1400hp).

I certainly wouldn't go out of my way to close the deck on a 2.3 motor unless it was the limiting factor... and I don't see that happening for any reasonable person, or the majority of people who are slightly unreasonable for that matter. Triumph's engine designers likely didn't close the deck for any sort of performance/reliability gains... these days it's usually about the most cost effective way to achieve the design goals, taking into account parts and services as well as manufacture and possible warrantee. Everything about the "jug cylinder" configuration over the individual sleeve set-up screams easier to assemble, easier to service, and more profitable to sell as replacement parts.

Just my opinion, of course

 

[Claviger]

I finally found what I've been looking for...

BigCC Racing did a custom GT35R kit on a standard years ago. It all went quiet after this post aside from selling a "stronger" crank for silly money.
Stock bottom end set to 10psi
Red is R3
Blue Is Turbo Busa


I agree completely about the economics being the likely culprit that drove the change. I don't intend to push the limits of the block ever, that power level would essentially be useless except on a drag strip, and even then it would be very hard to use.

 

[SpazOnaR3]

I

Good lesson in 'area under the curve' there... there is about 50% more work being done by the busa in those graphs if you work it out.

The stock motor on a G660 was an absolute animal at even 4 lbs of boost... I think I have that graph back in my old build thread. That turbo should be good for about the same amount of HP, but it comes on pretty quick... I think mine was making 200flt/lbs at 2800 rpm. Good on them for running the numbers uncorrected, though, that shows character.

 

[Gerald]

While I'm a fan of using extremes to test the bounds of an idea, sometimes we get a little apples-to-oranges. In my experience with stuff like this, I've started looking more at specific output and intended purpose for things, rather than what may be the 'pinnacle' of design or and idea.

A 2.5L engine making 500hp is impressive; call it 200hp per liter. While that number on a street going vehicle would pop eyeballs 50 years ago (turbos be ****ed), that is well within the design envelope for a lot of open deck engines. Comparing anything to an NHRA Top Fuel engine is lunacy... those engines are making over 1200hp/liter on a conservative estimate (some would say 1400hp).

I certainly wouldn't go out of my way to close the deck on a 2.3 motor unless it was the limiting factor... and I don't see that happening for any reasonable person, or the majority of people who are slightly unreasonable for that matter. Triumph's engine designers likely didn't close the deck for any sort of performance/reliability gains... these days it's usually about the most cost effective way to achieve the design goals, taking into account parts and services as well as manufacture and possible warrantee. Everything about the "jug cylinder" configuration over the individual sleeve set-up screams easier to assemble, easier to service, and more profitable to sell as replacement parts.

Just my opinion, of course

The thing I like about 2.3 engine is the replaceable cylinders, where if you needed to you could install replacement without step boring the cyl. and pressing in a sleeve, and likely distorting cylinders next to repaired one. But I do believe the 2.5 does offer more rigidity to allow for increased power levels.

 

[Nashvegas]

Kevin and Konrad were talking and what I took away, as an admitted engine-building dummy, was that replacing sleeves was ok in a “regular“ engine rebuild but if you were going with high-compression stuff just go ahead and get a lower, just like you would have to with a 2.5. Why risk a compromised lower-end when they aren’t that expensive. Kevin already had so many of the parts. “Oh, I already have those right here…” I have a spare quart of oil in my garage…

 

[Gerald]

Kevin and Konrad were talking and what I took away, as an admitted engine-building dummy, was that replacing sleeves was ok in a “regular“ engine rebuild but if you were going with high-compression stuff just go ahead and get a lower, just like you would have to with a 2.5. Why risk a compromised lower-end when they aren’t that expensive. Kevin already had so many of the parts. “Oh, I already have those right here…” I have a spare quart of oil in my garage…

I would believe they weren't against replacing cyl/sleeve, regardless of compression, but due to condition of engine, better to start fresh with a good known engine for a basis and perform the checks before starting the build. Nothing wrong with increasing compression on these engines. Just my thoughts, I'm not speaking for Kevin or Konrad.

 

[Nashvegas]

I would believe they weren't against replacing cyl/sleeve, regardless of compression, but due to condition of engine, better to start fresh with a good known engine for a basis and perform the checks before starting the build. Nothing wrong with increasing compression on these engines. Just my thoughts, I'm not speaking for Kevin or Konrad.

Yes, exactly.

 

[SpazOnaR3]

The thing I like about 2.3 engine is the replaceable cylinders, where if you needed to you could install replacement without step boring the cyl. and pressing in a sleeve, and likely distorting cylinders next to repaired one. But I do believe the 2.5 does offer more rigidity to allow for increased power levels.

Indeed, serviceable cylinders are nice touch... if you can keep a few extra.

In this case, I'll casually disagree with the 2.5 being any stronger until proven otherwise. While a closed deck would ultimately have a higher threshold for cylinder walk/shift/distortion if all other things were held equal, the block itself is ultimately weaker than 2.3 offering, what with it being split down the middle. At the power level that a closed deck becomes (more) necessary, you're going to have far more issues with cranks, transmissions, rods, and clutch components.... pretty much everything stock in that engine would likely fail before the cylinders started moving around enough to be an issue. If I were betting on it, I'd say around the 700-800hp mark at very high rpm is what it would take. and there is simply not enough chassis to put that sort of power down. Might be fun to find out one day, though.