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Someone here with an early 110 2.25P with the ACR powerplus kit?


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Last year I've bought a 5mb 2.25 petrol engine with a ACR automotive head fitted. It has a larger SU HS6 carburetor to give a little more BHP. I'ts in my 110 now, with a LT77 and a 1:1.4 transfer box attached to it. Especially in 5th gear I have the feeling thats its lacking power. Takes a long time to get up to 65/70 mph on the motorway. Probably because the 1.4 transfer box is a bit undergeared for the 2.25 engine, it came with a 1.6 originally. However, the low rpm is good to keep the noise down on. The transfer box will need to come of soon for some TLC, input gear is worn and new gaskets. I do also have a 1.6 lying around in the garage.. So I'm now in doubt what to fit. Is there anyone here that has the same setup that could share experiences with me? I'm especially curious to hear what the 1.6 box will do in terms of noise when driving at motorway speeds.

Oh yeah, Im running on 235/85 AT tires.

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Ehm yeah maybe ive used the wrong term. But anyway, Im trying to find the sweet spot between acceleration/power and the noise level.

Tried the ashcroft calculator this is what it tells me:

Current setup (1.4 box): at 120 KPH: 3060 RPM

Other box (1.6) setup at 120 KPH: 3900 RPM

Max power for this engine is around 4200 rpm i believe.

So the 2nd option should give me a lot more power for over taking etc on the motorway.. but the noise level worries me.

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No problem. The thinking is the velocity of air increases through the rpm range, therefore the turbulence within the carb increases which constricts airflow.

There is a book called "tuning the a-series engine" which focuses on the classic mini but it gives a step by step guide on how to modify carbs and the given cfm increase. As your engine is an N/A petrol you would be able to apply a lot of info in this book to your engine.

EDIT: I dug it out and took a few snaps, you can see on the graph it made an increase at the top end on a little 1100 engine

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post-8190-0-11251100-1441004500_thumb.jpg

post-8190-0-05689700-1441004560_thumb.jpg

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Thansk, very interesting info, ill try to get a copy of the book for sure.

But now back to the original question.

I assume ideally at cruising speed the engine should do as little rpm as possible, while still having enough power available to accelerate, right? Is there any way to determine this point? Then i would need to get hold of one of those torque/power vs rpm graphs i assume.

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I don't have an ACR full kit, but I have a 2.5 petrol with an ACR cam and a Turners 9.1 stage 2 head in my 1985 110 CSW (standard twin choke webber carb).

I run the standard (for 2.25 and 2.5 na 110s) 1.6 transfer box and 235/86 x16 AT tyres too. I run on LPG 99.9% of the time.

Yes, it is a bit noisy at 70 - 80mph, but not as bad as a TDi. A lot of the noise is wind/road noise. It is quiet below 50mph.

It does mean that the revs are continuously high on the motorway, but I drive mine to keep up with modern traffic and have been doing so for around 10 years with this set up.

Hope this helps,

Regards, Diff

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If the power is sufficient to drive in 5th on a flat road without a head wind, the gearing is fine. You shift down for other things like accelerating and hill, which is the point in having the 5 gears to choose from. Your not doing 80 with a 2.25 and all the gearing changes in the world are not going to get you there.

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Sorry SvBeek, I don't have a rev counter.

However, I have put the gearbox, diff and tyre specs, in Ashcrofts ratio calculator and it comes out with this:

Fourth at 70mph = 4382rpm, Fifth at 70mph = 3642rpm

Fifth at 80mph = 4162rpm

This is probably right, though the revs may be slightly higher in reality as I can just about hit 70mph in 4th if I rev it hard.

My Land Rover will do 75 to 80 mph on the flat in 5th providing there isn't a headwind. A motorway hill will see the speed drop off to 60mph in 5th.

Hope this helps,

Regards, Diff.

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