Franco

iTrader: (2)

I take it this is to do with throttle / fueling etc Stu........................

Gregs

got to be done! last time i let my lady drive us to a show (in our car cuz had a session the night b 4) i woke up with the road angel sayin 135 and an R1 next to us giving the thumbs up! have i got to tel her to stop that or what!!!!!

Franco

iTrader: (2)

Hope you went back to sleep!!

GARETH T

think about it,, as revs rise, the time available to get fuel into the engine is shorter

Mike Rainbird

iTrader: (3)

It's not so bad in a Sapphire, but an Escort takes a lot longer to get from 120-150 due to the aero-pack. Once you get up to this speed, rather than keep the throttle pinned, it is wise to lift off or the thermal build up can lead to a molten mess.

Obviously you won't have any issues if you have had it live mapped, checked and adjusted at these sort of speeds.

GARETH T

so you would think mike

Gregs

she was gutted when i told her she had no chance! the passenger on the back of the R1 was sh**ing it!

Anonymous

Ok, the term you need to learn to understand this one is "Peak Cylinder Pressures"


The peak cylinder pressure is (handily for once, lol) EXACTLY what it says on the tin.
Ie its the maximum number of PSI that is present in the cylinder at ANY point in the cycle.

Now we have the standard cycle (its easy to remember as its the same as having sex):
Suck
Squueze
Bang
Blow

Now during the suck, no problem, no pressure build up, no chance of gasket failure or the piston, squeeze the charge in the cylinder, same thing

Its a combination of the last two that is critical, the Bang and the Blow.



Now the explosion that happens in the cylinder, doesnt actually happen at all, what most people think is an explosion is in fact a burn, a controlled burn.

3 major factors influence the PCP directly

1 - number of moles of gas present
During this burn, you have an increase in the volume of gas, this is due to the fact that the burning process actually generates additional gas, as exhaust gas is given off from the burn. Ie after the burn there is a larger number of moles (no i have no idea why its called moles, lol) of gaseous molecules present that there are before the burn

2 - temperature of the gas present
The second is that there is a lot of heat generated, and when you heat a gas it expands (Boyles law, PV=NRT)

3 - the changing volume of the container
Now there is also a third factor that is going to effect the pressure that is VERY critical but many people overlook, and that is the changing size of space available for the gasses to fit into



Now the one we need to look at here, is just the third one really, as the other two arent greatly effected by a head skim or change in compressed gasket thickness



Right couple of basic observations:
the size of the area is changing based on time (well point in the cycle) as the piston moves up and down
the burn starts always before top dead centre on the piston.


Now put those two together and it gets quite interesting.

We start the burn off while the piston is still heading upwards, this means that the amount of gas present is increaseing, and the amount of temperature is increasing, and at the same time the volume of space available is DEscreasing.

What this means is a RAPID rise in pressure.

Now this pressure is trying to force the piston back down at the time, so you can NOT have it so that it occurs at TDC, cause if you did it would be exerting as much pressure to try and slow the engine down on the end of the compression stroke (you fire during that stroke dont forget!) as you have on the power stroke, and thats not good at all (plus it would cause Det, which i cant go into now or i will be sacked cause im supposed to be programming a toyota finance calculation at the moment not writing a ford essay, lol)

So where DO we want the peak PCP to occur?

Well this varies from engine to engine, but generally IME its 10 degrees or shortly after 10 degrees, if you are running lots of boost and the PCP is going to be massive at 10 degrees though, you may need to slide it as far as 20 degrees.
(this is another essay, as there is a trade off between effiency of the engine versus amount of moles consumed that is key to determining which you get max power from!)


Now, hopefully you are still with me at this point, and will have made the realisation that on your engine Stu has set the start of the burn (by setting the ignition timing) to a point in the cyle that allows the PCP to arrive at the correct point later on in the cycle.

So when you then go and change the volume of space available, you throw that completely up the wall!
You effect it in two dramatic ways, the more greatly compressed gas burns quicker, which drags the PCP further forward (which then increase the PCP value as the same amount of gas is present at a point with smaller volume), and the volume available all the way down gets smaller too, so the MCP (mean cylinder pressure, not sure if thats an industry standard term or not, but its one that suits me so im going to use it!) increases.


Now the danger in the increased PCP you are now seeing is that excessive PCP can cause detonation, which will nicely melt your pistons (or safety fuse group a head gasket, lol)

So thats one problem you face, a quick failure resulting from Det.

Now the other thing that no one seems to notice (well tuners do, but mere mortals dont!) is that the MCP i just mentioned will also increase, and with it so will the temperature in the chamber by the end of the cycle.


Guess what, the temperature at the end of one cycle effects the PCP during the next cycle.

congratulations, you just entered a viscous circle!




BOLLOCKS, just realised i wrote an essay based on the wrong topic, thats the one for the "can i skim my head or use a thinner gasket without a remap" topic. for me then!

I will write a little more now about the 803's



Ok, well looking back at that lot, you can see that ive touched on the subject of PCP management from one cycle to the next, this is where your 803's come into play.

Harvey is trying to run them nice and rich, so that the rich mixture burns cooler and keeps the temperature down, but at the top end of the rev range he cant do this, due to the short space of time available to fuel in, this results in a gradual increase in temperature, and hence (for the reasons above) an increase in PCP too, and eventually over time this temp increases to the point where you get Det.



I havent proof read that yet, as im really busy at work right now, so i will come back later and tidy it up a bit

Franco

iTrader: (2)

If i need my gasket doing

But very helpful!! As ever!!

Stu @ M Developments

iTrader: (12)

Top work chip

Hopwever, this is more what i was thinking.... https://passionford.com/forum/viewtopic.php?p=2246533

Anonymous

I did that same thing in chemistry A level mock exam once.


I got an essay back with a "F" on it.


I went to the teacher to complain about it.


He informed me that my essay was one of the most accurate and interesting essays he had ever read in 20 years of being a chemistry teacher and it was a crying shame it had absolutely nothing at all to do with the question he had actually set in the exam

Garage19

I was always taught
Suck
Squeeze
Bang (tech should be burn)
Fart

The fart bit instead of blow, is also more correct in the sex comparison for me. You can put slap in there after that too, but that has nothing to do with the four stroke cycle.

And i suppose bang makes more sense than burn otherwise you should be getting yourself down to the clinic

On a more tech note I always thought ideal angle for PCP to make most torque was 14-16 degrees?

Either way i canee prove it with out some serious kit

Franco

iTrader: (2)

ANSWER TIME!!!

Anonymous

Its in a different place for N/A than turbo, im more used to N/A

As i mentioned briefly though, can be as late as 20 in an N/A nitrous setup.

So your numbers sound perfectly likely to me mate

Anonymous

I kind of covered it at the end of the (wrong one ) essay mate, basically what you are risking is a build up of heat over time, so if i were you i would change up into 5th, rather than hang into it in 4th, and use the excellent midrange torque of a cossie motor to pull you along while still nicely in the range that harvey has mapped it.

Ie on your car i would "short shift" my way around the whole circuit one gear higher than i might in a car without this potential high RPM leanout.

Bet it makes almost bugger all difference to your time as well!

Franco

iTrader: (2)

so letting the turbo do the work & not the engine as such.........That right?!

Mike Rainbird

iTrader: (3)

Jason,
It's not as bad as Chip is mentioning, you can rev it to the limiter in all the gears bar fifth. In this gear do not hold above 6k for any long periods of time.

Franco

iTrader: (2)

Mike i didn't realise the aerokit had that much of an impact on a escort

Anonymous

I wouldnt be that confident that in 4th or even 3rd you can hold it flat out TBH mike, not on an uphill section anyway! (although at the ring there arent any really long uphills of course, so fair enough in that context only)

Basically Franco, what no one has told you and is actually the case is this:

Dont hold it full throttle anywhere that its not accelerating well still.


So as mike says, in 5th on the flat, 4th up a moderate hill, 3rd up a really steep one!

ballin

iTrader: (1)

really good read chip

Mike Rainbird

iTrader: (3)

The Escort was designed as a 120mph car, and the aerokit holds it back quite considerably (especially with baby power like yours ), so means that at higher speeds in fifth, you are having to be on the throttle longer to achieve the desired speed compared to an equiavalent powered Sapphire. This means the heat builds up quicker, due to the extra load the aeropack puts on the car with wind resistance.

Even with the standard 227bhp, the Escort with aero pack only does 138mph (compared to the 143mph sans rear spoiler). A 4x4 Sapphire does 145mph-148mph...

Garage19

I wouldn't say that unless you call big ol' lazy V8 american, I'm a redneck, pick up trucks competition vehicles?????

Greys were originaly used as a pair in production throttle body injection setups.

foreigneRS

not any long uphills at the 'ring?

you did do the full lap last time you were there didn't you chip?

you didn't exit at the adenau bridge (which would account for your lap time claims )?

Anonymous

Long = more than 10 seconds.

If you go so slow you spend 30 seconds on one steephill, thats not my fault


Cant win here really, if i said there were long hills mike would have said there werent, this forum is full of people who like to argue for the sake of it

Mike Rainbird

iTrader: (3)

The hill from the sharp right hander after the Adenau Bridge one, extends for some 1.75 miles . Hence why you struggle to pull any more than 135mph up it.... I'd say a FULL 30s on full load in 4th or 5th.

Eagle

iTrader: (2)

so ... after reading all of that .. it would be better for a bigger injector and longer cam combination ...

Mike Rainbird

iTrader: (3)

For top speed yes .

Franco

iTrader: (2)

Wry You no Wrisson!!

Eagle

iTrader: (2)

but even for normal use, an injector that is on less duty cycle is better so .. go for light blues or grey's ...

cossiedave

iTrader: (1)

ok so what boost can you run flat out on grays sorry to but in

Gregs

and what can you run flat out in greens?

GARETH T

you gotta remember guys that boost doesnt equal flow (and remember you fuel for flow )

so this question is inpossible too answer

Billabong

There is no general max boost for a given injector, as engine efficiency also has to be taken into consideration etc. It depends on your map and your engine (incl. turbo)

(EDIT: I MUST remember to refresh before replying )

cossiedave

iTrader: (1)

grays 7.2 comp 16 inlet std exh cams t4 it done 457bhp at power staion last week they said flat out in 5th would be 25 psi what do you all think

GARETH T

one fast car whats the max injector duration?

your not far off maxed i would guess,, theres lots of injectors you could ungrade too if more power is wanted

Charlie Chalk

iTrader: (1)

Will the top speed runs on 803's have the same affect on a cvh engine??



Ditto

Anonymous

...so basically cut all the talk on this thread and go back to my first replies..the subject was closed then!

cossiedave

iTrader: (1)

it is quite fast m8 puts a on my face anyway may be 8 greens next but there i would only get another 50 to 60 bhp and there gose the box

cossiedave

iTrader: (1)

boosh man y ant you repliad to my email buddy

Anonymous

...maybe cause...

1....i never got an e-mail

2....i dont like you

3....it was a stupid question

4.....you trying to help your mate out

5.....the Earth is rotating too fast

6...i aint gay

7....see above 6