JB only ran about 1.4bar with the gt30r. if the gaskets had let him run more boost the times would have been better.

at 1.4 bar the 30r felt far too big and the mid-range lacked real kick until 5000rpm. running about 1.7bar and the mid felt much stronger with the kick at 3700rpm. the 30r felt much more sized at this level until the gaskets pop.

john's 2.5 with 20g was a cracking road car and was stunning with the 5speed , even though the rev limit was not stretched back then , everything just felt right. the 6speed slowed his car down without a doubt ,leading to taller tyres and rev limits but we still could not match the balance of the first set-up. the 6speed is not ideal on my car either , this was highlighted recently when we compared my car to his M£ . from a rolling start I was that busy with the gearbox changes(not flatshifts) , that there was very little between them until 5th when I could stay on power and close in fairly comfortably.

alang's car is in a different league to jb's old 2.5/gt30r set-up. I would go as far as saying it is far too much for road use but it did show me what a proper 2.5/30r could do . with his gearing I think than if alan wanted to do a drag , the car would easily be a second quicker than mine up the strip and would think that hooked up ,it would do high 10's. dont know if the gaskets will like that sort of abuse though so he might be better staying away from the top speed runs , drags and dry track days

 

agreed , that is the best bit of the standard 2.5 , cheap torque to a sensible level. with the 6speed box though I would prefer a standard 2l sti block and heads to the standard 2.5 block for a standard higher hooligans rev limit.

 

I thought there were only 2 cats on a uk car dp and centre, just a dp one on a jdm car
But even adding a 2.5 short block to your suggestion, you would still struggle against a 2ltr jdm car, you need to understand the jdm car to understand why its better than the 2.5
And as for being emissions unfriendly.... yup for now but its not as far off as you think in comparison to a uk engined car! plus you have the low down torque and better gas flow from this engine over the 2.5.....
Now my point being, is instead of spending lots of cash on a 2.5, with some porting of heads and different manifolds, much cheaper option and similar performance in most cases (plus if you havnt sussed out why the 2.5 isnt up there in the big power stakes, have a look at BMW, they had a problem with their 6 cylnder engines in the late 80's early 90's?).
Remember, the only reason you have a 2.5ltr engine is that the size v emissions meet euro regs, theoretically its just as dirty as the JDM 2ltr.

Tony

PS, should add that the AVACS really does give the edge on these engines for low down torque, not just the size

 

tony,

have you driven a T25?

for a nice road car I would bet the T25 would be a nicer drive but for being the hooligan your spec-c will take some beating.

 

You really miss the point Tony (as usual ). I am not comparing a JDM to a UK car, I am comparing 2.0 to 2.5, which is what this thread is all about.

As for getting a JDM engine as a "cheap" solution you couldn't be further from the truth. For the price of a 2.5 conversion being done to a sensible car, you couldn't even buy a complete JDM enigne, tubro and ancillaries from a breakers.

And for the less well informed (Tony), the new age WRX (not sti) has 3 cats.

Put your car up against a T25 for an apples to apples comparison.
Paul

 

Tony, you having a laugh?

Alan Bell's car is a JDM Sti, and without a shadow of doubt, the car is a hundred times better to drive with the 2.5 engine.

 

Makes for interesting reading.

I would love to have a drive in a well setup std int 2.5l, but on paper at least I wouldn't swap out my std UK engine for one.

Maybe I would be of a different view after having driven one.

Personally I like to benchmark performance in terms of 1/4mile performance as I think it gives a good indication of quick a car really is, rather than RR plots. People can often be mistaken into thinking a 2.5l will be quicker than a 2.0l with similar mods and this has yet to be proven afaik.

As Andy has mentioned - 'feeling quick' and 'being quick' are two different things.


Bob

 

I can assure you, Alan Bells car, which weighs significantly more than yours Bob (especially compared to when you drag your car), is very impressive to drive, and in either my hands, Andy's or even yours, would be even quicker than the 12.9 it did in the damp at Melbourne nearly 2 months ago. (When you have seen Alan change gear, you will understand).

My old 2.0l would not keep up with Alans car as it is now, partially down to the better chassis, but the outright low down grunt it has is superb.

Steven

 

I had the fortune to go out in Gerry Houghton's 2.5 'cooking' Sti V3 with a 5 speed Sti v3 trans with AndyF mapping it.

That car had so much low down torque and it flowed into boost rather than rushed in.
When a turbo rushes in the car feels fast (Andy's 'wow' effect)
When it is smoother and low down to start the engine feels like a big capacity non turbo (bit like my 3200cc porsche)

Gerry's car is an API installation and his high mile road car; it was superb.
This was directly after Andy has mapped my Sti so close to a comparison i can get (as a passenger).

Graham.

 

Agreed it may feel quicker, are you saying it is significantly quicker than your old spec that was posting 12.0/1s? Maybe Alan will let one of us hooligans try his out at the strip to make for better comparisons?

I never feel a 2.0l is lacking in pull - when driving it fast you are always in the thick of the power, and there is no lag to speak of, when overtaking you may need to drop a gear or two which is where the 2 engines may differ.

Bob

 

You really are stuck in your ways bob!

1/4 mile times dont give you a very good idea of how quick a car is overall, just at peak power, the setup is worth so much more than people think too, just look at your car. If you want a car which is quicker on the 1/4 mile then save your money and buy a bigger turbo. if you want a car which is more driveable, has better throttle response and less lag (where lag is the time delay of boost, not threshold RPM) lower boost threshold, and a more linear feel, then get a 2.5.

You mention overtaking and it is situations like that the 2.5 really scores, or when you want to go through a series of bends without worry about keeping the engine on the boil by frantically going up and down a gear.

Your car has very little lag, but it's certainly there, especially when you want to floor it at 3500 when dropping a gear is often going to be quicker, but the 2.5 has already gone by then.

Paul

 

Correct Bob, i am saying it is significantly quicker than my 2.0l. It actually feels almost as responsive as when we chucked one together for TOTB, which did an 11.8, with the same gearbox as you, in the Lateral Sti5, in full trim, and that wasnt setup anywhere near properly.

I have to agree with Paul, you can use the 1/4 as the sole basis for deciding a quick car. What you use the car for most of the time has to be factored in somehow.

I would beat the hell out of my 2.0l day in day out, as i did the 2.5, but as a day to day car, i would choose the 2.5 engined one everytime, it offerred so much more when you were not wanting to be on the boil all the time.

Drag racing, you dont really care what your engine does below your lowest rpm drop point, but you do care what it does above that.

Day to day, you want the fattest torque curve you can get IMO.

Each to their own though.

Steven

 

FWIW (and I am not even attempting to get involved in which engine is better - lol ) I drove a 2.5ltr converted UK Newage STi last month tuned to 350/350 (fairly comparative). Tbh.... my 2ltr was (felt) a shedload more responsive, urgent and stronger..... but did require harder driving. Now, the 2.5 was on a single scroll turbo with standard UK Heads and Cams..... so not sure if that would make a load of difference as mine is a modded Spec C donkey.

Maybe not apples and apples.... but just thought I would add it to the mix.

Regards,
Shaun.

 

Just to highlight, the above was not a Type25, as I have STILL not managed to give one of these a punt yet..... IAIN!!!!!!??????

Regards,
Shaun.

 

On reflection..... forget what I said, as I just realised I have a weight advantage as well!!!

 

and we all know weight is a killer on 1/4 mile performance....

 

Thats why my 1/4 mile is only 12,9 my 17stones and a bugeye And could be my laid back gear changing ?? LoL, cheers Alan.

 

jeez, where's the RTM button gone? that webmaster geezer is just post whoring a decent thread!

 

Paul/Steven: If a 2.5 with std int and bolt ons can make reliable 11s with decent terminals then it sounds to be a good all round affordable package. This was why I asked the question as I wasn't aware of what it was capable on the strip. Are with talking cheap bolt-ons or more expensive rotated bits?

Paul: I would be surprised if a 2.5 would be gone if both cars were preparing to overtake at the same time. I tend to sit in gear at 3500/4000rpm waiting for the opportunity to pass - doesn't feel like any lag to me in this instance.

Also with regards to peak bhp being important on the 1/4mile and the benefits of the 2.5ls peak torque coming in early - I have peak torque by 4000rpm (RR in 3rd), which holds until 5000rpm and not exactly massive power either (340), so that plays down the talk of 2.0l+high rpm peak = quick 1/4mile.

Like I said I've not driven a 2.5l, so cant comment first hand. Am more than open to the idea of 2.5s though, hence taking an interest in the thread.


Bob

 

Steven: I think you missed the bit about standard internals.

 

i understand totally fella being a portly 16st 4 and a blobeye myself

 

The 2.5 doesn't need to prepare to overtake, that's the point.

If you are thinking of bigger turbo at the same time, then a 20g on a 2.5 is really quite special. It will pull better low down than your 16g on a 2.0, but still give you the added power the 20g offers at the top end. Have your cake and eat it, you know you want to!

Paul

 

mmm, 20g cake .....

 

Be interesting to hear the views of someone who has had both. Doesn't make sense (to me at least) to spend ££££s on a 2.5 block, 20g +fmic to achieve pretty much the same times/terminals. I have absolutely no issue with the 16g - I find it very nice for the road, so it would take something worthwhile (good 1/4mile improvement for sensible money) that would be quicker on the strip without sacrificing road driveability. Regarding road performance - I recall John commenting that he couldn't shake T-uk, John being in the 2.5-20g/GT?? and T-uk in the 2.0-16g

John, care to comment on your experiences of 2.5l+20g vs 2.0l+16g. If you were to do it all again what would you do for an everyday road car?



Bob

 

with your 5speed , I would take the standard int. 2.5 and 20g everytime over my 2 16g.

with tall gearing , even UK heads might work quite well as they will bring the peak power down lower than sti heads would, possibly peaking like a standard MY00-TD04 car , which will mean there is no need to rev over 7000rpm

 

Bob,

Who said anything about an FMIC? With 20% more torque, 15% more power, less lag and a lower boost threshold, do you really beleive it will be slower? The reason we don't see plenty of 11 second 20g cars is of those running few drag race them, and of those that do, very few are prepared to put the effort in that you do.

Remember that a 2.5 will offer NO guaranteed improvement in 1.4 mile times, as the power is ultimately limited by the turbo. The 2.5 simply means you can maintain your current response with a larger turbo that allows more power. On the road the 2.5 is completely different to drive, more flexible and more relaxed, but again, if you are prepared to work with a smaller power band you can be as quick.

I think you need to work out what you want from the car rather than to keep asking if product X will suit your as yet unspecified exacting requirements.

Paul

 

..

 

You seem to have made your own mind up and want someone to tell you you're right in doing so.

What insight are we supposed to get from John's post? That the 2.5 with a 20g is no quicker than a 2.0 with a 16g? To me it says that JB was no quicker than T-UK despite a more powerful car (which incedently weighted about 100kg more too).

 

done quite a few road car builds where the only variance is the block/internals i.e. 2.0 or 2.5.......................

the one that was most astonishing was a simple 2.5 bottom end conversion on a 99spec UK car (albeit with Pace front mount GEMS ecu and VF34 as these were already fitted)............although ultimately the turbo isn't large enough at the top end and requires a gear change around 5500rpm, it builds seemless boost from 1700'ish and hits over a BAR by 2300-2400, it peaks at 1.4BAR and holds this until 5000..........all on the std 2port

any gear any speed and the response is instant, even 5th gear autobahn overtaking from 50-60mph is instant and 120+ appears pretty much as soon as you like........

in the real world, where you don't always know where the next overtake, etc. is then i would take this sort of route everytime

alyn

 

Bob

I have to agree with Paul here, having run my type R on a 2.0 with a 20G against John Banks's UK 2.5 with a 20G.
I can assure you when we were alongside each other preparing to "go" I even had my foot on the brake, building boost at 4krpm when the signal was given then the 2.5 just immediately pulled away by 2-3 car lengths

With Alans car on the 2.5 I think the best way to describe it is it feels like a lightweight RA with a very fit 2.0 Now, put this fit 2.5 in a lightweight RA and you would think it would make it into a flying machine ....but the reality is that the gearing kills it as you have to shift cogs so frequently, negating many of the gains.

I think key to making a 2.5 work well in a classic is the gearing, ideally even longer gears than the std UK ratios.

Andy