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Omega Help Area => Omega General Help => Topic started by: laney101 on 05 February 2018, 07:27:32

Title: Caters tuning guide question
Post by: laney101 on 05 February 2018, 07:27:32
Read through the whole caters tuning guide on internet other day and a lot of it is information from this site?

Main thing asking was it was stating putting 2.5v6 heads on 3.2 block matching the ports and using 3.2 head gaskets raises compression a bit allowing more power and linking with 4xg cams made quite a good cheap power hike


My question is what would sticking 2.6 heads onto a 3.2 do ? I'm guessing the chamber is smaller than a 3.2 so would still raise compression so why not use these instead... Or is it the 2.5 are smaller again allowing higher compression than a 2.6 head ......
Title: Re: Caters tuning guide question
Post by: omegod on 05 February 2018, 12:54:01
I think the only difference between 2.6/3.2 is the length of stroke
Title: Re: Caters tuning guide question
Post by: LC0112G on 05 February 2018, 13:20:41
My question is what would sticking 2.6 heads onto a 3.2 do ? I'm guessing the chamber is smaller than a 3.2 so would still raise compression so why not use these instead... Or is it the 2.5 are smaller again allowing higher compression than a 2.6 head ......

EPC says the X25XE and Y26SE share the same cylinder head part numbers, including valves, springs and camshafts. So it appears to me the engine top end is identical.

Con rods are the same too, and EPC lists the same crankshaft p/n, so stroke must be the same although the bearing part numbers are different for some reason? However, the main difference appears to be that X25XE blocks use 81.6mm diameter pistons, whereas Y26SE uses 83.2mm diameter pistons. That's a 3.96% increase in surface area so for the same stroke it raises a 2.5L to 2.599L. So looks like a simple block overbore job to me. It therefore follows that any reduction in compression ratio must be due to lower piston height.

Never seen either in real life, but that's what the part numbers say.
Title: Re: Caters tuning guide question
Post by: Marks DTM Calib on 05 February 2018, 16:20:00
Camshafts are NOT the same but the cylinder heads are from 1998 onwards (when an additional web was added to allow the coil per plug setup to be screwed into place....same is true of the 3.0/3.2 heads)
Title: Re: Caters tuning guide question
Post by: LC0112G on 05 February 2018, 17:49:43
Camshafts are NOT the same but the cylinder heads are from 1998 onwards (when an additional web was added to allow the coil per plug setup to be screwed into place....same is true of the 3.0/3.2 heads)

Well, my 2001 version of EPC and the online version both agree that the X25XE and Y26SE use the same camshafts, although there is a change to both dependent on engine number.

Inlet = 90509845 (NLS) superceeds to 90512905 at engine number 08077074
Exhaust = 90509846 (NLS) superceeds to 90512906 at engine number 08077074

https://opel.7zap.com/en/car/v94/e/4/35-0/#1

There is a different p/n listed (24456229) but no details on when/where it's used. NLS anyway.
Title: Re: Caters tuning guide question
Post by: laney101 on 06 February 2018, 09:14:40
So basically dropping a 2.6 head on my 3.2 will do what I'm wanting raise compression .. Just make sure I fit 3.2 exhaust valves as sodium filled and 3.2 cams or 4xg...


Anyone any idea how much compression will be once 2.6 heads are fitted ... According to quide a 3.2 with 2.5 heads give around 10.8.1 which is good improvement overstock allowing more ignition when super unleaded being used
Title: Re: Caters tuning guide question
Post by: Kevin Wood on 06 February 2018, 09:26:16
You need to do the calculations. IIRC, I worked it out a few years back and it was going to result in too much compression but it's possible that was for a 3.0 bottom end not 3.2.
Title: Re: Caters tuning guide question
Post by: Marks DTM Calib on 06 February 2018, 10:46:56
Camshafts are NOT the same but the cylinder heads are from 1998 onwards (when an additional web was added to allow the coil per plug setup to be screwed into place....same is true of the 3.0/3.2 heads)

Well, my 2001 version of EPC and the online version both agree that the X25XE and Y26SE use the same camshafts, although there is a change to both dependent on engine number.

Inlet = 90509845 (NLS) superceeds to 90512905 at engine number 08077074
Exhaust = 90509846 (NLS) superceeds to 90512906 at engine number 08077074

https://opel.7zap.com/en/car/v94/e/4/35-0/#1

There is a different p/n listed (24456229) but no details on when/where it's used. NLS anyway.

I have rebuilt a fair few 2.6's (for stem seals) and none of them used the E and F cams
Title: Re: Caters tuning guide question
Post by: Marks DTM Calib on 06 February 2018, 10:48:13
You need to do the calculations. IIRC, I worked it out a few years back and it was going to result in too much compression but it's possible that was for a 3.0 bottom end not 3.2.

I had some calcs and it gets it to very close to the 3.0, putting them on a 3.0 would certainly raise it to high :y
Title: Re: Caters tuning guide question
Post by: Nick W on 06 February 2018, 10:54:22
So basically dropping a 2.6 head on my 3.2 will do what I'm wanting raise compression .. Just make sure I fit 3.2 exhaust valves as sodium filled and 3.2 cams or 4xg...


Anyone any idea how much compression will be once 2.6 heads are fitted ... According to quide a 3.2 with 2.5 heads give around 10.8.1 which is good improvement overstock allowing more ignition when super unleaded being used


You do know that standard management uses the knock sensor to retard from the preset ideal, not advance to it?
Title: Re: Caters tuning guide question
Post by: Marks DTM Calib on 06 February 2018, 11:18:46
So basically dropping a 2.6 head on my 3.2 will do what I'm wanting raise compression .. Just make sure I fit 3.2 exhaust valves as sodium filled and 3.2 cams or 4xg...


Anyone any idea how much compression will be once 2.6 heads are fitted ... According to quide a 3.2 with 2.5 heads give around 10.8.1 which is good improvement overstock allowing more ignition when super unleaded being used


You do know that standard management uses the knock sensor to retard from the preset ideal, not advance to it?

The Bosch setup advances until knock is detected and then retards by 2 degrees before repeating again, it will adapt quite nicely.  :y
Title: Re: Caters tuning guide question
Post by: laney101 on 06 February 2018, 12:28:04
Indeed apadpts nicely obviously to a point however I will be going standalone management/piggyback ecu at same time so can be mapped properly...

So that is no issue to me... However don't want it so high that even 99octane fuel isn't enough to make use of the compression haha

3.2 is lower comp than 3.0 or 2.5   so I would think fitting smaller cc head would raise it but not to level of that on a 3.0 .... Anyways shall see haha

I'll strip 2.6 heads down rebuild fit 3.2 exhaust valves reshape ports to match 3.2 manifolds and have chambers and valves coated
Title: Re: Caters tuning guide question
Post by: deviator on 06 February 2018, 14:00:08
I have rebuilt a fair few 2.6's (for stem seals) and none of them used the E and F cams
Didn't the Vectra 2.6 sri have E & F? I know the GSI got 4 x A.

To the OP, G's for BHP A's for torque (apparently). Or combine the two. I seem to remember reading the power comes in later with all G's.
Title: Re: Caters tuning guide question
Post by: laney101 on 06 February 2018, 15:26:34
Don't a 3.2 have G inlet and J exh ... I'm sending a set of 3.2 cams of to be reground by newman cams
Title: Re: Caters tuning guide question
Post by: deviator on 06 February 2018, 15:39:04
Don't a 3.2 have G inlet and J exh ... I'm sending a set of 3.2 cams of to be reground by newman cams
I think it depends on what car the 3.2 came from, I seem to remember one had H and J. IIRC the H & the J are great, at holding doors open  ;)
Title: Re: Caters tuning guide question
Post by: Marks DTM Calib on 07 February 2018, 09:04:08
The cams are not wildly different, the 3.0 and 3.2 had a 1.2mm higher lift  and the G's a slightly longer duration.

I did dial gauge them all to get the profile but, cant find the results.

Its clear the 2.5 and 2.6 were throttled back using the cams, the lift on the 3.0/3.2 means the valve curtain area is pretty much exactly equal to the valve throat area so pretty optimal.
Title: Re: Caters tuning guide question
Post by: laney101 on 14 February 2018, 06:03:58
As far as aware all 3.2 omega have G and J cams ideal for torque and power good balance...

Gonna grab a spare set and send away to be reground