2.8 build best cam profiles????

[JAFF]

as above ,im building a 2.8 stroker ,iv been reading the 2.8 wiki page , just wondering which is the best cam profile and what people are running successfully ? as i dont want it to sound over lumpy but want to it to breath better on standard springs

[toby]

Check goosieganders thread for his 2.8 build.

[JAFF]

yep done that toby ,was just wondering what others may have been used ,272-272 etc

[Gunni]

What compression are you running?

What do you actually want out of this engine?

Why do people post vague questions?

[JAFF]

not sure that its that vague ,just a question to open conversation as to what people are running and there thoughts on different profiles ?
with regards to compression iv not a clue! im simply following threads iv read to get the bits i need and so on ,
im not after a race engine as per say but something thats better than your average 2.8 but with out going into major cost and with out putting strain on the engine at the same time ,the thread on wiki says cams anywhere between 270-276 ,id be intrested to read what you think Gunni

[Gunni]

You need to have a power goal in mind.

Without one you can buy anything and then be annoyed it´s not working like you hoped.

Thats why having a goal people can help you determine if what your after will be obtainable at all given some restrictions.

If you run something like a 280cam you should be able to run 11:1 compression and get out of the engine what you want with running optimum ignition with 98octane fuel.

So are you prepared to run 98octane or vpower all the time?

[JAFF]

whats sort of performance would i expect to get from using a 272 cam to be very honest it would be unlikly that i would fill up with vpower or 98 all the time and if thats a consideration in the big scheme of things then it would be best just to skip that idea straight away

[DmcL]

@ Gunni, could he not run say 95 octane fuel with a 272 and 11:1 comp by running less agressive ignition timing? i would have thought it would be a matter of deciding what cam, installing it and any necessary supporting mods then tuning it to run on whatever fuel he wants it to run on primarily and tune ignition timing so as to avoid detonation?

FWIW ive actually got a couple cams up on ebay atm, a schrick 272 and a kent 277. not entirely sure what im doing with them.. may use one myself or may just sell both as i would like to go turbo down the line which would mean removing whatever cam i put in when the time comes so im not sure if i should bother using one till then or not.

[Gunni]

But that´s not good engine building, to purposely hold back the engine design with ignition timing due to running the incorrect fuel for the setup

[sweep]

so a 2,8 wont run normal unleaded

[Gunni]

Nobody is saying that, but if you want to make use of a high lift cam then upping the compression is a good idea and too high of compression and any engine wont run on normal unleaded.

[daimlerman]

So to run stock UK unleaded,what is the suggested C/R and max cam lift?

[DmcL]

But that´s not good engine building, to purposely hold back the engine design with ignition timing due to running the incorrect fuel for the setup

yea i know its not ideal but it can be set to run on typical 95 octane.

if u really wanted to go whole hog with it a switching device could be built and used with a 512k chip with 2 tunes on it. one tune could be watered down for 92-95 octane and the other could be set for 98 octane so whenever the extra power is wanted just fill up with 98 and flip the switch for the 98 octane tune. would be easier to live with on a daily basis if it wasnt purely limited to running only on 98 octane fuel.

[JAFF]

wow mind boggle !!! so if i run a 272 cam or anything other than stock i need to use super unleaded ??????

[Gunni]

No ,

the compression ratio is the major factor here.
If you end up with 10 you´ll be fine.

If you run 12 you won´t be.

[sweep]

with a 2,8 ecu and 270/272 cam how will it idle ? will it be higher than a stock 2.5 engine?

[JAFF]

ok simple terms then gunni ! i have 2.8 injectors the rest is as per the wiki link ie b20 rods b25 pistons but with a complete seal rings ,what cams would you say would be best for 1: normal fuel and 2: 98 octane

[eta]

Which pistons are you using. Early one give you a higher CR than later ones. If you have not decked the block 0.5mm your CR will be lower than that quoted in the wiki.

To give you an idea. I have a 2.7i with eta pistons a CR of 9.35:1 and with a stock 325i cam I get peak power at 5900 rpm. Putting a fancy cam on this engine is unlikely to make much of a difference ( a few hp at the top end maybe and lower low end torque/power). If you are using later pistons you will have a CR of (~9.5:1?) So again not very high. running 98 fuel won't give you any power advantage so sticking a high lift cam will just lower you low end torque for a few Hp at the top end.

You run high octane fuel on high CR engines so still run the optimal ignition advance with detonation.

[JAFF]

i need to check the pistons when they arrive as i have brought them from fowler with the piston rings that span right around the piston ,do i need to deck the block ? Or can I leave it standard

[HairyScreech]

2.5 and 2.8 low comp pistons and high comp pistons, also a 0.5mm skim accounted for if using 130mm rods and wanting stock piston placement.

[JAFF]

man im confused ! im going to use 130mm rods with 2.5 pistons ,can i have a simple yes or no to having the deck skimmed by 0.5mm if thats the case do you then use a thicker gasket or is that pointless ,i need a spec sheet it think

[eta]

Yes skim the block by 0.5mm, then your CR will with low CR pistons will 9.856:1 as posted or if you use early pistons you will get 10.92:1 for which high octane fuel will be must along with a RR mapped chip or standalone management. You will get the best from an upgraded cam with a block skim.

[JAFF]

thanks for your help ,just awaiting the rods and pistons to turn up then to find the right crank
may need your advice further when they arrive