the only real difference between my car and jb's 2.5 with 30r was his aircon. both cars where stripped similarly and my gut probably equal's his aircon.

thinking about this a bit more. jb driving my car does mid-high 12's , in his own with 20g or 30r he was doing low-mid 12's

 

JB and BMW deserve each other

 

I thought that was at a time when John's boot was ICE'd up and he had the 6 speed to your 5 (I know later you got a 6 speed though).

Paul

 

I am sure the BMW service manager will think that too , when anything needs done.

have to laugh at the "I need something a bit more subtle" so he gets the bling mobile with it's 19's, flared arches ,bright red leather , 4pipes out the rear, bling rear lights and bell end bonnet bulge , just about flattened it the other day , chasing him up the farm road with the L200 and that does not like corners too.

paul,

both cars stripped and ran on the same day , both with 6speeds.

 

Bob, FWIW you have got better results than many with your relatively cheap spec. As you know I don't have a clue about drag racing but I think your time is quicker than most can achieve with a much bigger and costlier spec. So your dilema seems to be that you may upgrade, to find it won't let you go any quicker, even if it feels faster and goes quicker in the real world of traffic etc.

Basically I think you made a quick car first time for not much dosh. This may not be the case for the next stage and there is no proven spec to do what others can't already do on more exotic and expensive engines!

F

 

Bob, your results are extraordinary, so it makes recommendations difficult, especially when I can't do the quick gearchanges without breaking things and couldn't get good launches on the GT30R.

I think the 2.0 on 16G is a benchmark for a balanced road car. The 2.5 on 20G takes the same attributes and scales them up a little at higher cost and with more hassle. For a new age where you can buy a car with it in... I don't recall running the 2.5/20G against T-uk's 2.0/16G but with drivers of similar ability in cars of similar weight and suspension/brakes, I think he would agree the 2.5 has no disadvantages as long as the gearing is correct. It is cake and eat it as you just get a fatter power band IMHO whilst still on a 20G unless you run a built engine when you could exploit the moments of brilliance the 2.5/Ion for example had when running 25 PSI just before the headgaskets went and a piston cracked. It walked past T-uk's car when he was maxxed out in a surprising fashion in a shortish distance, in much the same fashion that he likes doing suicidal speed on his single track farm road (you have to get your seatbelt on before he launches the L200 as otherwise the hilarity and g-forces - as well as the pain from his dog's claws tearing up the $krotum as it hangs on for dear life - that you can't get it done until he has completed his special stage mud bath suicide mission and tried to knock down the porch he doesn't like...)

For a nice, easy, reliable road car, IMHO don't make the mistake of messing up the gearing or throwing too big a turbo onto it.

For a drag monster, I'm crap at it so ask someone who can... Andy and Pavlo!

 

Bob,
My 2.5 with STI3 heads and a TD05 20g was running high 12's all day ET 108'ish (first time drag racing) I was trying to launch gently Final result placed 17th at SSO. Not bad for my first DIY engine build

I suspect with a bit more mapping and someone who can actually 1/4 mile it would make it into the 11's

 

I still think the next logical step for bob is a 20g and if he finds the road drive compromised too much , then he could fit a 2.5.

assuming he can fit just the 20g and match andy's old 2-20g improvements , then I am sure he could get a similar gain if not more , if he later added a 2.5.

I still suspect the biggest question will be over the head gaskets on a hard used 2.5 even if not going over 1.4bar. I think at k/hill , jb ran around 1.2 bar while I was peaking to 1.7 and holding 1.4, rolling at the top. both cars lasted but we doubt the 2.5 would have at my boost.

 

I'm not at all convinced drag racing is a true measure of this debate.
A run over country from a to B is dependant on driver skill/risk/ and a hundred other factors.
For my experience up a 1 mile hill climb my Sti before all the 20g and stuff, the car was faster with the Sti gearbox than an RA trans. Same engine/driver/track/weather conditions ie dry.
I spent ages changing gears everywhere.
The same car with Sti trans and the '20g' 2 litre is 2 seconds faster up the same hill etc.
That's 315 bhp/280 lbft verses 380 ish x 340. It is the torque hike that gives the punch low down out of the bends providing you are above 4500.
Much earlier Bob'5 said he held the car at 4500+ rpm waiting for the slot to overtake and had zero lag.
Do that with a 2 litre and a 20g and the pick-up is astonishing as 1.45 bar arrives super quick.

Surely any hike in torque and hence power, will make for a quicker car?

Bob'5 clearly has found/made a great 2 litre as the results show on the strip, a 2.5 that can rev and pull longer gears due to torque would improve the times further.

Graham.

 

Gerry Houghton runs 1.4 midrange on his 2.5 20G and he does fast track work with it (Bedford/Bruntingthorpe) including some 20k/year daily driving and it's been fine for a good while now.

 

Steven, you mentioned Alan Bell's 2.5 was running a TD06 based turbo, is this a TD06 20g not the 25g version that seems to be popular in the States on the 2.5. How would the TD06 20g compare to the TD05 20g on the 2.5, would this be the equivalent to running a 18g on a 2.0

The TD05 20g caused surge problems on the 2.0 when rotated according to Harvey ( to eliminate the early 90 degree turbo entry ) would this still be an issue on the 2.5 ?

Colin.

 

Alan has a TD06-49 which is a garrett compressor wheel.
The 06 turbine driven turbos (pretty much regardless of compressor wheel) on a 2.5 spool in a similar way to a TD05 driven compressor on a 2.0

The 20G compressor will surge on either 2.0 or 2.5 if you feed it with a big bore inlet pipe.

Andy

 

I couldn't make the 20G surge on the 2.5 with MRT inlet pipe even with lots of boost low down or part throttle full boost, although I don't think I tried it with a stiffly sprung dump valve. Certainly not a hint on full throttle.

 

We still get a bit 'chuffing' on Gerrys car but def better than a similar large intake set up on a 2.0

 

Seems as if this thread has turned into a major hijack - apologies, wasn't intended this way. Just keeping my eye out on what people have done and with what results, so that I have an idea of which direction to proceed if I do decide at some point to go further with the car.

Also some of the questions raised may give answers to some topics people have not asked of the 2.5 conversions that 'most' seems to default to after an engine failure.

Some of the pitfalls:

1. Reliability - seems to be many head gasket problems
2. Gear Ratios - with the 2.5 capable of producing good torque, most will require a stronger box. The 6-speed seems to be the choice of many, probably down to cost/strength (it still isn't cheap). It seems the 6-speed ratios don't seem very well suited to 2.5s, from what I can gather.
3. Insurance - When I asked my previous insurer (L&V) about a 2.5l they said it would double the premium.
4. The assumption that a std 2.5 will be quicker/better than a std 2.0.


The ratios aren't a concern for me as mine are probably better suited than a 6-speed. Reliability is a concern - will a std 2.5 handle the abuse my std 2.0 takes, at the sort of power levels that will make a faster car on the road and strip?
Then there is also the issue of how much power is really needed for the road - I find mine more than adequate for the road as it is, particularly in these conditions.

The sensible side of me says "if it's not broke, then don't fix it and if it does break then simply fit a replacement 2.0l (STi9) and stick with the same spec". If the 2.5s reliability wasn't in question and they were well 'proven' that would also have to be a route to consider.


Bob

 

is there no way of making a 2.5 closed deck block thats as strong as the 2.2, 2.33 etc?

 

not as strong, but yes there is a way.

There is one such shortblock in my engine bay.

For 6k it is yours!

 

why is it not as strong? and sadly....im not in the market

 

You can liner it, like this (cdb)


http://www.crawfordperformance.com/p...nfo.cgi?id=147

 

theres some standard liner photos on the axis site, which show why the 2.5 is not as good as the 2.0 and 2.2

2.0


2.2


2.5

 

Why is it that the 2.65 engine never gets spoken about?
I would assume with the right turbo and supporting tweeks that would be very torquey and enough to frighten everyone's gearbox, even Bob'5.

I believe Crawford is highly respected, but those liners must be very thin at 2.65 litres, but they can't be too fragile or they wouldn't sell them.

Graham.

 

so do you have the Rally spec one andy? being 2.33(4)?

 

I thought I saw a 2.8 on thier site too

F

 

yup, looks pretty funky, dont think id be too keen on the pricetag mind....

 

The one I have is not available any more, its based on the centre one in the pics above, note also the main bearing support and piston oil cooling in addition to the thicker liner and bore top support.
The 2.65 has thick steel liners which provide more bore strength than the alluminium supporting the thin liners on the 2.5.

 

Whats the donor for the 2.65 cdb?

 

Well said that man!

That'll be the reason why i've changed then.

 

Were these power runs done in 3rd or 4th gear? The images say gear 3

The power curve on my 2.5 (20g) conversion looks different in that, the power justs keeps rising towards the redline and the torque remains flatter once it peaks, only really starts to drop off at 4900rpm but in a gradual slope.

My car is running 1.2bar makes 336bhp and 315lbft. Peak power is at 6600rpm and peak torque 3600rpm

Powerstation rolling road 4th gear

I will post the jpeg later when I can scan it.

Andy