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c20xe tuning guide?

40K views 22 replies 10 participants last post by  SimonT 
#1 ·
Seems everone is ranting about how lovely the C20XE engine is, and they´re probably right!

But I can´t seem to find a good sensible tuning guide for some reason.
What´s the C20XE good for, and what are the logical upgrade steps for a good track setup without burning a hole in my wallet?
 
#7 ·
Still no tips on a possible upgrade path for the C20XE?

How much will, say, a chip + cams + 4-2-1 manifold give me?

Are internal modifications required if I intend to go weekend racing @7000 rpm?

Are those SFI box mods really beneficial to BHP/torque or does it just add noise?
Even my company car sounds quicker without the air filter but in fact it isn´t :)
 
#8 ·
check out the BHP calculator in the downloads section for a rough idea of power.

and on the standard rev limit the engine will strong enough for racing as mine goes racing all the time (with cams, exhaust, and aribox mods) and is fine.
 
#9 ·
cams are a tricky subject on the c20xe as the bestcams means that the pistons hit the valves which means new or machined pistons with bigger pockets. but the other mods o make a difference get your self a nce mainifold/front pipe makes it go better. but watch out with induction kits as i am sure most people will tell you they mess the smoothness up on the engine. haven't done a chip myself cause iam saving for tb's for real power upgrade.
mat
 
#11 ·
hmm... upgrading an C20XE. First the little easy stuff.

lose the cat.

look at a larger manifold, there's a 'budget' one from sbd (150+vat) which makes a noticable difference.

remove the 'orange segment' from the main throttle plate.

clean the injectors

As far as air filters go, I'd avoid a cone style filter, and go for a panel filter and drilled airbox with some extra ducting.

There's plenty more gadgets available, powerboxes etc, but GM spent a lot of time and money (on cosworth) designing the XE, and the SFI box is there to improve midrange torque, if you remove/replace it, and you'll find it hard to regain that torque.

As the XE's cams are quite perky as standard, there's only a few profiles available which'll work with a standard induction system and no internal mods. courtney do a (by all accounts) good regrind, which is quite cheap. I think the std cams are 274 degree duration, the 285 profile cams need pocketed pistons.

if you want to get dirty, the best budget mods for an XE is rehone and new rings, as most 100k+ xe's won't be making as good compression as they could. new big end bearings will be good at the same time, and valves lapped etc. all that lot is not too hard, given enough time, an haynes manual, mig, and a few choice expletives, it should be managable for an enthusiast.

if you want to spend serious money..... than the world's your oyster, with turbos, superchargers, TB's all available for the XE.
 
#12 ·
ok so how much would you be looking at for a rebuild of an xe with a bore out to 2.1 (like Mikes), other mods to allow for wacky power and revs at a later stage, like lightening/balancing etc? Omega pistons alone are around £400 aren't they?
 
#13 ·
depends on how far you want to go.

rebore is somewhere between 50 and 100 quid, crank regrinds about 50 for mains and 45 for big ends, balancing 20-50 quid, big end shells either 23 quid a set, or 92 quid a set, depending on which you go for. mains are about 25 quid a set.

'wacky power' mods are generally pocketed pistons and ARP big end bolts.

look at sbd's site for other prices.
 
G
#20 ·
Animal
There's plenty more gadgets available, powerboxes etc, but GM spent a lot of time and money (on cosworth) designing the XE, and the SFI box is there to improve midrange torque, if you remove/replace it, and you'll find it hard to regain that torque.
Are there any RR figures to show that you lose bottom end power and where you lose it.

As you say above then just before that say remove the 'orange segment' from the main throttle plate, Did cosworth not think about this too. Is it not there for a reason?

I am thinking about getting a power cap for my nova 16v conversion so really I need to know what effects it will have, also I have no room for a standard air box so I will need to use a cone filter.

I have a cone filter on my cav and suffered no ill affects or lose of power.
 
#21 ·
lee may said:
Animal


Are there any RR figures to show that you lose bottom end power and where you lose it.

As you say above then just before that say remove the 'orange segment' from the main throttle plate, Did cosworth not think about this too. Is it not there for a reason?

I am thinking about getting a power cap for my nova 16v conversion so really I need to know what effects it will have, also I have no room for a standard air box so I will need to use a cone filter.

I have a cone filter on my cav and suffered no ill affects or lose of power.
For RR figures, I saw some somewhere awhile ago on corsasport, you do gain power by removing it, but it changes the torque curve quite a bit. If i drop an std XE in the manta, I'll have to remove it too, needs must etc.

The orange segment is there for drivability, to make medium throttle opening more gradual, if you're after a bit more power, that's an easy trade off.

The cone filter is a bit of a lottery, it works for some people and not others, which is why i suggested the air box.
 
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