Where can I read the pressure on that graph? 4psi seems very low. But as you have a DTA and probably the correct pressure/voltage relation for the sensor, you should be able to calibrate and get a reliable pressure reading.
The pressure/voltage relationships are in the workshop manual, which I believe you have
I seem to remember having read somewhere in there it has 0.5 bar (about 7psi). I read it electronically, I didn´t print the manual. Can´t quite find where I read that. LPT´s normaly are in the range of 6psi. I quote 4psi as ridiculously low :-D
will it hold?
I believe so.
IMO (and from a book I read ;-) ), it is only at a small part of the cranks´ revolution angle beyond TDC, that the resulting cylinder pressure (inducing tensile loads) will see higher values in turbo guise than the maximum value it will ever see in NA guise. Yes, loads will be higher beyong TDC, but only during a small part (say 30°). And even than loads are only 20 up. This is because power and intertia loads are acting on the conrod and they are equalling out one another. Only, the unbalance inthe turbocharged case is a little bigger than in NA.
Am I missing something here?
The compression ratio on that lump in 9.2:1, that's high for a turbo lump, mostly cus it was designed for economy and low CO2 emissions, not for high pressure boost, cus all the torque is right on the bottom end, ideal for the 75's slightly portly weight.
boost is the light pink line at the bottom.
the pressure reading was made by the very accurate rollers. might not be that as std on all, but this one was. if not then that is a much better result than i expected.
the pressure will also rise in the cylinder before the piston gets to tdc. as soon as the inlet valve closes (iro 50 cam degrees after piston has passed BDC) the compression stroke starts.
estimated dynamic compression ratio on 4psi is 9.9:1
on 7psi it rises to 11.5:1 compression.
quite a difference.
roughly, the engine made 170bhp at 5252rpm. that would equate to 170lb/ft torque.
so if you wanted 200bhp at a the same rpm you would need 200lb/ft torque.
now, BMEP, is the average (mean) pressure which, if imposed on the pistons uniformly from the top to the bottom of each power stroke, would produce the measured (brake) power output.
bmep = (150.8xtorque lb/ft)/displacement Ci
displacement = 109.567Ci
BMEP for 170lb/ft engine = 234psi
BMEP for 200lb/ft engine = 275psi
ring land just under the top ring will take most of that pressure.
the std engine is quoted as 160lb/ft torque = bmep of 220psi. so you would be adding 25% more pressure to the piston/rods to get 200bhp/torque.
not sure rover would have gone that high on their parts specs.
all calculated as ive not tried it myself so may well be wrong. but imo 200bhp is the upper limit on the engine in std guise.
I would say too much, if you can crack 180 in using standard rods pistons and liners I'd be very impressed. Look a the T series 'bo, that's a HUGE heffer of a lump for a reason.
Me, personally, after 8 weeks, I've fallen for the KV6, especially that resonating growl when the VIS opens up..thirsty she may be, but by god, I'd drive that car till my feet were naught but stumps on my ankles.
BMEP calculations are merely used as a BHP comparison tool. The formula does not give you residual stress imposed on the crank or rods. My point is that the "25%" increase in piston pressure does not equate a 25% increase in stress or tensile loads on the ancillaries. TBQH, I don´t know how to calculate the load increase. I´m environmental, not mechanical. But I´m working my way through it ;-)
9.2:1 is not as high as you might think.
The Merc SLK230 compressor, the Eaton M62 roots blower generates up to 7 psi at a C/R of 9.5 (air/air IC). But then the roots blower has a higher thermal efficiency than a gas driven turbine.
Saab´s 9-5 2.3litre estate has a C/R of 9.3:1 and runs a turbo at maximum 8psi with an IC air/air
FYI, when using a compressor, I found this table of what can be achieved (without being fool proof that is) w/o intercooling. I admit, numbers are quite high.
Final Compression Ratio (FCR) = (Boost / 14.7) + 1) x CR
Boost = Maximum Boost
14.7 = Psi. at Sea Level
CR = Engine Static Compression Ratio
The ZT-T was conceived to be a tax beater. Don´t know the regulations in the UK for a car to be a tax beater. But I bet emission and KW are part of it.
I also know a guy who has been driving his BBR LPT (7psi) Turbo charged air/air IC MGF (no internal mods whatsoever) for 4 yeas now, without it skipped a beat. But then, bet he wasn´t a track day fanatic.
I only know they use big (VVC) bearings and the pistons from the "mexican" type VVC. I once posted the partn° on a popular thread on X-power forums. I believe this (pistons) had to do with emission regs in mexico. From the EPC I also noted a different partn° for the gasket (over the other NA gaskets)
That´s about it.
I´m currently doing a LPT conversion on my K and tend to keep the pistons and other ancillaries. Might use a thicker gasket (Ferriday Eng) to get downto 9.5:1 regions (I already have the gasket). Will keep you posted on progression. But I don´t have the intention to trash is on the track or nurnburgring though ;-)
How are you doing with your 1.4K-T :-D
My guess is that mine won´t be fool proof. But then we´re no fools right?
mexico must have very low ron petrol then or are they running on sugar cain? think i remember a top gear when they were running their cars on absolutely anything they could lay their hands on. im sure i saw shampoo in one of them!.
yeah ive fitted a copper gasket to another K build. was a sholar evo4 block though.
mines not too bad, started cleaning the bearing ladder, got me bearings out of the boxes, got 3 missing
do a bit each week, heads all built up, just trying to sort the block now.