T5 vs PX engine (NOT basic tuning)

[GiulioEX125E]

Hi everyone!

As usual, sorry in advance but I don't speak german so I'm writing in english since most of you can understand it (I hope).

 

So I am here to ask a simple question: considering the same "tuning level", can a T5 engine have the same performance of a PX engine?
I can use the example of a PX engine that I built recently:

 

187 Malossi MHR, 127-190°

28 or 34mm carb, vforce4 reeds on bolted-on MRP block

LML cases heavily welded and milled in the intake area to have a big area for the mixture to come in

60x110 Tameni crank

Pipedesign Bullet + Megadella XL (used both - not at the same time )

 

GSF dyno showed something around 27-28hp (the exact value is irrelevant, we all know it can also show 35hp if I change some values...). But even ignoring the hp value, generally speaking I assume we all know how an engine like this can perform, more or like.

 

So I'm curious of what can be achieved with the same level of tuning, but starting with a T5 base. Example:

 

Malossi 172 cylinder (I think it's the only "good" one for T5), timings around 130-190° or something like that

bolted-on reed block, no welding

28 or 34mm carb

long stroke crank (still no idea which one, its all hypotetical)

expansion chamber exhaust or box exhaust (Megadella XL, BGM BBS, something like that - not interested in Polini box, Sip Road etc)

 

Do you think something like that (I know the engine description for the T5 is very generic), can perform as good as the PX engine, with the same level of tuning?

More specifically... I'm interested in a T5 project because the T5 engine is the natural evolution of the PX engine, so it has a "stronger" crank, a better bearing for the flywheel side, and last but not the least, it has bigger transfer ports. Regarding transfer ports specifically, I also would like to do something like this, if it is possible: welding the area as in the picture, both on the cases and on the cylinder, to have a bigger surface so that I can mill even bigger transfer ports; this way the would start looking similar to a modern 2stroke engine, where the transfer ports usually are really huge. Original T5 ports are already big, but since this welding and milling work isn't so expensive or complicated to do (I hope!), I would really like to try.

 

 

 

 

 

So short version:

1) do you think PX and T5 engines with the same tuning level, can achieve the same performances?

2) what do you think about the welding & milling idea for the maxi transfer ports?

 

Thanks in advance :)

Bearbeitet 23. Januar 2022 von GiulioEX125E

[Phantomias]

Hi, the T5 is the better engine as you stated. Instead of welding and modifying the T5 Malossi, I would use the Pinasco 251 cylinder + 60mm crank.

[GiulioEX125E]

1 hour ago, Phantomias said:

I would use the Pinasco 251 cylinder

The 251 Pinasco surely is an interesting cylinder, I especially like its huge transfer ports (way bigger than a Quattrini 244 for PX, for example) but I have 2 major doubts on it:

 

1) 251cc (and all big bore in general) produces a lot of torque, I don't think the original Piaggio T5 cases would last long. It would probably be needed to use Pinasco T5 cases, that are reinforced on the cluster area, where PX and T5 cases usually crack

2) the price of the Pinasco 251 is higher than the Malossi 172, and as stated in n.1, it would also require the reinforced Pinasco T5 cases (in my opinion) so the price would be even higher

 

So you think the 172 Malossi for T5 isn't a good cylinder? If raised to around 130-190°, do you think it has less potential than a 172 M1X / 177 VMC Stelvio / 177 Malossi MHR, for PX?

Bearbeitet 23. Januar 2022 von GiulioEX125E

[Vic]

take a look when you are thinking of heavy modifications:

 

 

[Phantomias]

Hi, to lower the torque you can use less stroke. I am not sure if the Pinasco Carter has a better quality than the Piaggio. 

 

For the Malossi 172: more than 30HP are possible if you increase the stroke (57mm?) and do porting. Welding is not necessary and might destroy the engine casing. Will you try using the rotary inlet?

More than 57mm stroke is difficult because the cylinder is quite short, but you can overcome this partly with another piston with a different position of the top ring. 

 

You could also try converting a BFA225 cylinder for T5.

Bearbeitet 24. Januar 2022 von Phantomias

[GiulioEX125E]

4 hours ago, Vic said:

take a look when you are thinking of heavy modifications

Nice, I will surely give it a read! Thanks

 

2 hours ago, Phantomias said:

I am not sure if the Pinasco Carter has a better quality than the Piaggio

As far as I know (never had them in my hands), Pinasco T5 cases have more material on the cluster area, which is already a huge upgrade from Piaggio cases.

 

2 hours ago, Phantomias said:

Will you try using the rotary inlet?

I would prefer reed intake, because I already have everything it needs. Also I have very limited experience in rotary intake, and finding the best timings would be quite a pain...

 

Overall I think this T5 project would cost too much for a small (if any) performance increase from my current PX engine. Piaggio T5 cases cost quite a lot, Pinasco T5 cases even more. There is no garantee that a 172 Malossi would perform better than my current 187 MHR on PX, and the only relevant difference would be the bigger transfer ports. Uhmmmm the more I think of  this T5 project, the less smart it sounds