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The Cosworth FAQ - by Mike
Rainbird
Q. What boost is a standard
Cosworth supposed to run ?
A. All Cossies (3-door / Sapphire / 4x4) with the exception of the
Escort are limited to 10 psi (just under 0.7 bar) and will hit a
severe boost cut if they see 11psi or more for anything more than
a couple of seconds. The Escort has a limited over-boost facility
that will allow the car to briefly see almost 15psi (1 bar) in the
midrange before it backs off to 10psi.
Q. What is the maximum boost
that I can run on standard injectors?
A. In all cases this is a constant 15 psi (1 bar). At this level
the injectors are wide open and would not be able to supply any
more fuel to go with the increase in air if the boost was raised
above this level. Also at this amount of boost you have also reached
the limit of information that the standard 2 bar MAP sensor can
provide. To allow the Escort to overboost as it does it has a 2.5
bar MAP sensor instead of the normal 2 bar item.
Q. Why if it is a 2 bar
MAP sensor can it not provide information for 2 bar of boost?
A. You are forgetting that normal atmospheric pressure is already
1 bar, so a two bar MAP sensor can provide information for "normal
atmospheric" (1 bar) + 1 bar = your 2 bar. Same with a 3 bar MAP
sensor, this can provide information for "normal atmospheric" (1
bar) + 2 bar = your 3 bar.
Q. How come some conversions
run much more than 2 bar of boost, yet still get away with using
a 3 bar MAP sensor without blowing up?
A. Now comes the clever bit. People like Ahmed can actually go beyond
the MAP limit by extrapolating the air ratio curve into the chip,
thus filling in the portion of the curve where the MAP sensor ends.
Q How much boost can I run
through a standard turbo?
A. 21psi 2wd / 24psi 4x4 / 27psi Escort. Anymore than that will
overspin the turbos and cause the bearings to wear prematurely.
Q. Is it worth uprating
the intercooler?
A. Yes, even on a standard 2wd car you can see improvements by fitting
the later (50% larger) 4x4 intercooler with no other mods. This
provides a more dense charge air (the cooler a gas is the more of
it fits in a defined space) and gives effectively "free" bhp. By
that I mean that the engine is not anymore stressed than it was
before the mod, you have just made the intake system more efficient.
4x4 intercooler equiped cars can be replaced with RS500 size Pace
items and the Escort Cossies can have their chargecooler systems
seperated from the engine cooling.
Q. What bhp can the transmission
take?
A. On the 2wd cars the gearboxes and diffs are good for 480bhp+.
However, if you are doing lots of standing starts the diffs cannot
take more than 380bhp before they become unreliable. The 4x4s however,
can only take up to 350 bhp in both the gearbox and diffs before
things start breaking. Third gear is normally the first thing to
go, followed by the front drive shafts.
Q I have heard that it is
hard to change gear from 3rd to 4th on 2wd cars?
A. This is a common fault and is just the baulk rings getting worn
on the syncros. These need replacing every 30-60,000 miles depending
on how it has been driven.
Q. How easy is it to get
power out of a Cossie?
A. It goes like this (2wd). A chip, actuator and 15psi of boost
will release an extra 70bhp (commonly referred to as a "stage 1").
A chip, actuator, higher flow (803) injectors, 3 bar MAP sensor
and 21psi will release an extra 110bhp (stage 2). A chip, actuator,
803 injectors, 3 bar MAP sensor, hybrid turbo and 27psi will release
an extra 140bhp (stage 3). An engine dyno re-map, 803 injectors,
3 bar MAP sensor, bigger hybrid turbo and 34psi will release an
extra 180bhp (stage 4). A chip, actuator 403 (grey) injectors, 3
bar MAP sensor, T4 turbo and 21 psi will release an extra 220bhp
(stage 5). To go above this or equal it with a smaller (more responsive)
turbo would require head work and cam changes, as well as "blue-printing"
the engine for reliability.
Q. What is the most bhp
that can be gained out of the different injector types?
A. Standard yellows (2wd) / dark blues (4x4) is 200-270bhp. 355s
(light greens) 270-300bhp. 803s (dark greens) 300-385bhp. 400s (light
blues) 370-430bhp. 403s (greys) 400-450bhp. After that you need
to go to eight injector set ups to get above 450bhp. Please note
that the ranges given, are the lowest and highest power figures
you would ideally use the injector for.
Q. I have heard that the
Escort Cosworth fuel pump is not very good?
A. Yep, this is true. For some reason Ford skimped on this and put
in a pum not really man enough for the job. This means that it has
to be replaced beyond a Stage 1 conversion, whereas all the other
Cossie fule pumps are sufficient until another set of injectors
are required.
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