Saxperience - Citroen Saxo Forum - View Single Post - JP's 220+bhp NA 16v Mango Westcoast

Sandy309 · 23rd January 2012, 08:24

The engine spec is pretty much finalised in my mind, but if I learn anything from my other engines along the way, that can be applied, then I will. The main thing for me is, whatever I decide to do with it, it needs to be reliable and low risk. Josh lives along way from me, so popping over to take a look if he has any problems/concerns, won't be possible. On that basis, I won't be doing it as a "Stroker". I have another customer locally that has asked me to do one and accepts the risks, so I'm evaluating it for his engine currently. The thing is, "Stroker" engines do not give you free power. The old saying "No substitute for cubic inches" is largely true, but when you're pushing the constraints of an engine that's already pretty much maximised, you can lose alot of what you gain, let alone the cost of parts.
I have alot of data already to draw on, from my other work on other engines, but to give you a broad idea of the numbers involved, here goes:

Standard engine: 78.5mm bore x 82mm stroke, 1587cc
Typical oversize: 80mm bore x 82mm stroke, 1649cc
Stroker engine: 80mm bore x 89mm stroke, 1789cc

If you're planning a fast road kind of engine, with hydraulic followers, the restrictions of rev limit and valve sizes are unlikely to be a problem, but for a race spec engine; it is a problem. The valve sizes I use in my race engines fit on the standard JP4 valve seat inserts, if you want to oversize the inserts (properly!), you'll be adding around £500 and the exhaust port will limit you anyway, there isn't enough material in the head to port to suit sufficiently big exhaust valves, for a free spec 1800, you'd have to make a compromise.
Regarding rev limits, we come up against the issue of piston speed and thrust angle. Peak piston speed and rod thrust angle will provide a glass ceiling for performance; beyond a point, frictional losses and wear become excessive; curbing performance and reducing engine life.

Probably not the best example, but perhaps the most extreme, is the Honda B18C. It's a more sophisticated engine in many ways that the TU and Honda went to a great deal of trouble to make the 8600rpm rev limit possible, including a very high spec big end bearing material. It has 87.2mm stroke and 138mm long con rods. That means, that at the rev limit, peak piston speed is 41.2m/s (24.7m/s mean) and rod thrust angle 18.4 degrees. That is very much on the limit of what you can practically do with regular high quality parts. That's about the same rev limit as i've settled on for my race TUs, as being durable and reliable, 8600rpm. A standard stroke TU5 with cup car spec rods (as most 1600s use), will give peak piston speed of 38.5m/s (23.2m/s mean) and rod thrust angle of a nice and steady 17.3 degrees. If we apply the same thinking backwards to an 89mm "Stroker" TU with 133.5mm rods (to make room for the stroke), we get a rev limit of 7840rpm and a rather worrying rod thrust angle of 19.5 degrees.
So if we assumed both the standard stroke (80mm bore) engine and stroker (80mm bore) engines operated to the same maximum piston speed and could both make 87lbft/litre at that peak speed, they would in fact; make the same power, 230bhp. Reality is, that the TU 16v head is very tricky to optimise for that level of performance and there aren't many engines genuinely in excess of 210bhp out there, with a decent torque curve anyway. Considering the very risky rod angle too, I'm not convinced a stroker kit offers good value. The other interesting aspect, is that there is a long stroke crank in the Peugeot range, that can be used, with modification and that's the route I may be testing elsewhere.

Getting back to the spec of Josh's engine, outline shopping list is as follows (SB=Sandy Brown, CS=Colin Satchell):

TU5JP4 block and crank
SB+CS steel flywheel, 7.25" race clutch
SB custom steel h-section rods
SB custom design pistons
Peugeot Sport sump baffles
SB ported and prepared head
SB custom single piece stainless valves
Piper double springs and retainers
SB custom solid followers
SB custom cam profiles
Alloy vernier pulleys
Steel belt rollers
SB+CS race spec GSXR TBs inlet design
Twin injectors
SB custom exhaust manifold (Stainless) and system
DTA S40 ECU and SB loom
Built, dyno run in and mapped by SB.

Every journey starts with a single step and here are some before pics, of the donor engine:

Block my need a little paint! There are many aspects of the engine I won't be showing in detail I'm afraid, but here's a sneak of my pistons:

23rd January 2012, 08:24	#886
Sandy309 Regular Poster Join Date: Jan 2010 Location: Cornwall Posts: 349 Car(s): 106 XSi	The engine spec is pretty much finalised in my mind, but if I learn anything from my other engines along the way, that can be applied, then I will. The main thing for me is, whatever I decide to do with it, it needs to be reliable and low risk. Josh lives along way from me, so popping over to take a look if he has any problems/concerns, won't be possible. On that basis, I won't be doing it as a "Stroker". I have another customer locally that has asked me to do one and accepts the risks, so I'm evaluating it for his engine currently. The thing is, "Stroker" engines do not give you free power. The old saying "No substitute for cubic inches" is largely true, but when you're pushing the constraints of an engine that's already pretty much maximised, you can lose alot of what you gain, let alone the cost of parts. I have alot of data already to draw on, from my other work on other engines, but to give you a broad idea of the numbers involved, here goes: Standard engine: 78.5mm bore x 82mm stroke, 1587cc Typical oversize: 80mm bore x 82mm stroke, 1649cc Stroker engine: 80mm bore x 89mm stroke, 1789cc If you're planning a fast road kind of engine, with hydraulic followers, the restrictions of rev limit and valve sizes are unlikely to be a problem, but for a race spec engine; it is a problem. The valve sizes I use in my race engines fit on the standard JP4 valve seat inserts, if you want to oversize the inserts (properly!), you'll be adding around £500 and the exhaust port will limit you anyway, there isn't enough material in the head to port to suit sufficiently big exhaust valves, for a free spec 1800, you'd have to make a compromise. Regarding rev limits, we come up against the issue of piston speed and thrust angle. Peak piston speed and rod thrust angle will provide a glass ceiling for performance; beyond a point, frictional losses and wear become excessive; curbing performance and reducing engine life. Probably not the best example, but perhaps the most extreme, is the Honda B18C. It's a more sophisticated engine in many ways that the TU and Honda went to a great deal of trouble to make the 8600rpm rev limit possible, including a very high spec big end bearing material. It has 87.2mm stroke and 138mm long con rods. That means, that at the rev limit, peak piston speed is 41.2m/s (24.7m/s mean) and rod thrust angle 18.4 degrees. That is very much on the limit of what you can practically do with regular high quality parts. That's about the same rev limit as i've settled on for my race TUs, as being durable and reliable, 8600rpm. A standard stroke TU5 with cup car spec rods (as most 1600s use), will give peak piston speed of 38.5m/s (23.2m/s mean) and rod thrust angle of a nice and steady 17.3 degrees. If we apply the same thinking backwards to an 89mm "Stroker" TU with 133.5mm rods (to make room for the stroke), we get a rev limit of 7840rpm and a rather worrying rod thrust angle of 19.5 degrees. So if we assumed both the standard stroke (80mm bore) engine and stroker (80mm bore) engines operated to the same maximum piston speed and could both make 87lbft/litre at that peak speed, they would in fact; make the same power, 230bhp. Reality is, that the TU 16v head is very tricky to optimise for that level of performance and there aren't many engines genuinely in excess of 210bhp out there, with a decent torque curve anyway. Considering the very risky rod angle too, I'm not convinced a stroker kit offers good value. The other interesting aspect, is that there is a long stroke crank in the Peugeot range, that can be used, with modification and that's the route I may be testing elsewhere. Getting back to the spec of Josh's engine, outline shopping list is as follows (SB=Sandy Brown, CS=Colin Satchell): TU5JP4 block and crank SB+CS steel flywheel, 7.25" race clutch SB custom steel h-section rods SB custom design pistons Peugeot Sport sump baffles SB ported and prepared head SB custom single piece stainless valves Piper double springs and retainers SB custom solid followers SB custom cam profiles Alloy vernier pulleys Steel belt rollers SB+CS race spec GSXR TBs inlet design Twin injectors SB custom exhaust manifold (Stainless) and system DTA S40 ECU and SB loom Built, dyno run in and mapped by SB. Every journey starts with a single step and here are some before pics, of the donor engine: Block my need a little paint! There are many aspects of the engine I won't be showing in detail I'm afraid, but here's a sneak of my pistons: