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(Post Link) post #1 of 27 Old 09-04-09 Thread Starter
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2.5 v6 engine tuning

i have a few questions, i intend at some point to improve the performance of my 2.5 v6, i would like to do the following
it wont be for a while yet, i will probably start when the cambet gets done in about 8k miles

fit the larger intake runners
upgrade the induction, probably gsr pipe (i hear good things)
3.2 of 3.0 cams (if i can get them cheap enough)
exhaust is already done
suspension is already done

remap? can this be done on mine 98 s reg?

i will be upgrading the diff to a q2 and upgrading the brakes somewhere along the line too

any recomendations on stuff to do/not to do?

mainly the advice i need is on the cams and remap as i know very little on these subjects despite reading many threads on the subject

also is it worth doing some work to the flywheel while the gearbox is off for the q2?
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Re: 2.5 v6 engine tuning

3.0 cams are no different, only the 3.2 inlet cams are.
 
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Re: 2.5 v6 engine tuning

There's a 3.0 engine and box going in the F/S section, I'd buy that rather than faff about with a 2.5
 
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Re: 2.5 v6 engine tuning

We can fit 3.2 cams and remap to suit(you have a M2.1 ecu,so its a soldering job) does make quite a difference
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Re: 2.5 v6 engine tuning

whats the contrast between 3.2 cams and intake runners with a remap and fitting a 3.0, is there any big cost/perfomace difference?

cheers for the input
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Re: 2.5 v6 engine tuning

If you buy a 3 ltr,na matter what you pay for it you will still have to fit it with new belt and tensioners which you will be doing on the 2.5 when you change cams and you will still have to remap the 2.5 ecu to run the 3 ltr.
Also if you buy a 3ltr you have the cost of labour for fitting it
So,the only differences are the cost of buying cams for the 2.5 or the cost of buying a 3ltr engine.
You can now work out what suits your pocket best

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Re: 2.5 v6 engine tuning

The 3.2 in mine is being run on standard management. I think the fueling is OK but I do think that a remap will liberate more power.
 
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Re: 2.5 v6 engine tuning

i wont be able to afford to do things all at once, so i will most probably fit the intake runners and sort the induction then when the cambelt is due i will have the cams fitted at the same time and if funds allow i will also have it remaped at the same time

what kind of gains would i expect to get after the work is done?

also is it worth having the flywheel lightened at the same time as having the q2 fitted? will it dive me a reasonable gain after the engine work is done?

also could you give me a rough idea of costs for the cams and remap?
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Re: 2.5 v6 engine tuning

Get the 3.0 fitted, its a 30 horsepower hit straight away and a shedload more torque. I drove a decatted and tweaked 2.5 back to backwith my 3.0 and the difference between the 2.5 and the 3.0 was very noticeable, the 2.5 just did not have the same 'get up and go', although it did feel pokey at the top end that was about it, gutless through the mid-range.
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Re: 2.5 v6 engine tuning

If you buy the 3.0 you will have a lot more to play with, in fact, you can do all the things you want to do to the 2.5 except for the runners. Q2, cams, intake, etc. Of course, you would need to sell the 2.5 to recover some of the money, otherwise it's a lot of money spent on car upgrades.
 
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Re: 2.5 v6 engine tuning

i was thinking the cost of buying and fitting a 3.0 engine would possibly be too much for my finances where as if i upgrade my 2.5 i can do it a bit at a time

what kind of power increase do you think i would get with intake runners, cams and remap? would it be close to the 3.0 engine?

i would imagine it would still be very a very different beast to the 3.0 but is it a worthwhile thing to do?
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Re: 2.5 v6 engine tuning

I would have thought the cheapest way you could do this is to look out for a 166 or GTV V6 that has failed its MOT or been crashed and is for sale. Preferably one with recent cambelt job done, then you can use the engine and sell the rest of the bits to repay some of outlay on the car. But it should cost you no more than 500 for the car anyway.

OK you will have to pay someone to do the swap.
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Re: 2.5 v6 engine tuning

With intake runners and re-map you will gain 20hp according to sqaudra tuning... thatl take power to 210hp... and with cams, id say you'l have anything between 220 - 230 hp... Thats 3ltre power....
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Re: 2.5 v6 engine tuning

Dawie says he built a 2.5 156 that runs with gta's, That sounds promising!
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Re: 2.5 v6 engine tuning

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Originally Posted by N2Oxide View Post
Dawie says he built a 2.5 156 that runs with gta's, That sounds promising!
hmmmm.....

i doubt mine will ever be that quick (would be nice though) as i probably couldent afford to throw that much money at it

220 - 230 will do me very nicely indeed

i can get hold of the intake runners, i just need a cheap source for the cams

anyone have any idea where/how much the cams will cost?
i will try my local breakers next time im passing

cheers for the info N2O
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Re: 2.5 v6 engine tuning

You'll be lucky to get the cams in a breakers, they know how much the engines are worth as a whole. You may have to bite the bullet and order them from the dealer.
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Re: 2.5 v6 engine tuning

ive been reading various things here and there (reading is a dangerous passtime ) what would be the benefit (apart from the sound of a screaming arese engine) of raising the rev limit to say 9000 rpm and what would be involved with it obviously the conrods would need replaceing but what else? can the crank, block and heads take that kind of abuse or is it just a lost cause? (i told you reading was a dangerous passtime )
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Re: 2.5 v6 engine tuning

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Originally Posted by pcbuild2k View Post
ive been reading various things here and there (reading is a dangerous passtime ) what would be the benefit (apart from the sound of a screaming arese engine) of raising the rev limit to say 9000 rpm and what would be involved with it obviously the conrods would need replaceing but what else? can the crank, block and heads take that kind of abuse or is it just a lost cause? (i told you reading was a dangerous passtime )
Obviously you would need to have the car remapped etc, and fit cams with longer durations on the intake cycle, but you could effectively raise the power output just by increasing the rev limit. You would need forged pistons and conrods for the engine to be able to take it though, and modifications to the intake and exhaust so they weren't so restrictive. Power is a product of torque times revs. Torque is mostly a product of engine size, or how much air you can get in. Increased rpm is like pedalling faster on your bike..

190bhp at 6,500rpm = 153.5lbft torque.

If you had the same torque at 8,500rpm you would have 248bhp.

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Re: 2.5 v6 engine tuning

The 2.5 will lack torque no matter what mods you do to it, I would save up your cash and buy a 3.0 V6 instead.

I have all the parts on my 2.5 that you have mentioned except the cams and although the engine is more powerful its not a patch on the torque and power from the 3.0

But if you have a good 2.5 engine already with recent cam belt change then its hard to justify the cost and risk in fitting an unknown 3.0 engine
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Re: 2.5 v6 engine tuning

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But if you have a good 2.5 engine already with recent cam belt change then its hard to justify the cost and risk in fitting an unknown 3.0 engine
But with a recent cambelt change already its hard to justify doing it again to fit GTA cams..
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Re: 2.5 v6 engine tuning

9000rpm would cost a vast amount of cash, rods pistons, possibly crank, huge amount of balancing work, solid lifters, block girdle, new timing belt system. You could maybe build a pair of 3.8 engines for that sort of outlay

Either buy a 3.0 or another type of car
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Re: 2.5 v6 engine tuning

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But with a recent cambelt change already its hard to justify doing it again to fit GTA cams..
true
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Re: 2.5 v6 engine tuning

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You could maybe build a pair of 3.8 engines for that sort of outlay
in that case, i wont be going down that route

i wanted to stick with the 2.5 as i know the history of the entire car, i know the engine has been looked after (regular oil and filter changes etc.) since new as i knew the previous owner very well, he had the car for around 6 years and lavished all his attention on the car, so i know i have a good engine to start with, 62k miles when i got it most of which were motorway use and now on 92k miles again mostly motorway use, also due to my limited income at the moment i would like to do things a bit at a time, another reason an upgrade to a 3l engine would be tricky for me (i would like to get a 3l though )

so if i can get a few bits here and there once i replace the cambelt in around 8k miles time i can get things like cams fitted at the same time to spread the cost out (or at least thats the plan)

so what do you guys think would be the best solution?

should i just stick to the idea of trying to get the intake runners and cams along with a remap and q2?

thanks for all the info so far
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Re: 2.5 v6 engine tuning

Its a worth while upgrade if you can get the parts at a good price, much of this stuff comes up for sale once in a while on here and ebay.

How much are a pair of GTA inlet cams?
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Re: 2.5 v6 engine tuning

If you have a cambelt change due sometime soon, then you need to decide sharp-ish what you are going to do. Maybe it would be best to fit the GTA intake cams, along with the bigger inlet runners from the 3.0 or 3.2. Decat it, sort the intake out and get it remapped. But its still not going to be a fire-breather, maybe you would be better off selling it and buying a GTA for 4-5k or so, much more bang for your buck I reckon.

Alternatively, do all those mods and top it off with a 100bhp shot of NOS.
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