1.9 Gti On 40's

[taffycrook 2]

There have been quite a few people asking if 40's can be used on the 1.9.

I had a set of 40's lying around and a 1.9 gti to put them on.

The engine was in fine fettle last time it was set up and made 133 bhp on the same rollers.

 

The carbs were jetted to suit and fitted with 32mm chokes. After a couple of runs to sort out the ign timing a power curve was taken.

 

On the track and road this set up pulled well and seemed very torquey. But seemed to hit the wall at 5500 rpm. The power curve mirrored this feeling with peak power at 5350 and peak torque at 4800.

 

figures were 125 BHP and 174 Nm (130 lbs/ft)

 

This goes some way to prove that although you can use 40's on the 1.9 it is less than ideal in terms of power. 34mm chokes may of produced a bit more power but not enough to make it worthwhile.

Edited November 22, 2006 by taffycrook

[christopher 5 1 Cars]

There have been quite a few people asking if 40's can be used on the 1.9.

I had a set of 40's lying around and a 1.9 gti to put them on.

The engine was in fine fettle last time it was set up and made 133 bhp on the same rollers.

 

The carbs were jetted to suit and fitted with 32mm chokes. After a couple of runs to sort out the ign timing a power curve was taken.

 

On the track and road this set up pulled well and seemed very torquey. But seemed to hit the wall at 5500 rpm. The power curve mirrored this feeling with peak power at 5350 and peak torque at 4800.

 

figures were 125 BHP and 174 Nm (130 lbs/ft)

 

This goes some way to prove that although you can use 40's on the 1.9 it is less than ideal in terms of power. 34mm chokes may of produced a bit more power but not enough to make it worthwhile.

 

 

Taffy isn't 32mm very small for a 1.9? I'm using 34mm on my 1.3

 

How was the low end torque?

 

 

What about 36mm?

Edited November 22, 2006 by christopher

[PumaRacing 1]

There have been quite a few people asking if 40's can be used on the 1.9.

I had a set of 40's lying around and a 1.9 gti to put them on.

The engine was in fine fettle last time it was set up and made 133 bhp on the same rollers.

 

The carbs were jetted to suit and fitted with 32mm chokes. After a couple of runs to sort out the ign timing a power curve was taken.

 

On the track and road this set up pulled well and seemed very torquey. But seemed to hit the wall at 5500 rpm. The power curve mirrored this feeling with peak power at 5350 and peak torque at 4800.

 

figures were 125 BHP and 174 Nm (130 lbs/ft)

 

This goes some way to prove that although you can use 40's on the 1.9 it is less than ideal in terms of power. 34mm chokes may of produced a bit more power but not enough to make it worthwhile.

 

Nonsense I'm afraid. 40's aren't restrictive up to about 150 bhp and that's plenty for a mildly tuned or std 1.9. Whatever the problem was it wasn't in the carbs.

[Hilgie 16 2 Cars]

Agreed. I had a mildly tuned 1.9-8V on twin 40 Dellortos and it did 145bhp on the rollers.

[taffycrook 2]

Christopher I used the set up that the carbs came with just to see how well it would work. I have no doubt bigger chokes would work up to a point but 36mm chokes don't work very well on 40's.

The torque spread it very good across the usable rev range which is 1000-5350.

 

Puma when you say nonsense do you mean the results or the fact that a DHLA 40 is too small for a 1.9 8v. The engine is in fine fettle and made good power on injection, there might be a bit more to come in terms of ign timing as it was pinking to begin with and I had to back off the ign. If 99ron was used it might be better. In an ideal world i would of tested using 34mm choke but I dont have any. I have had fast road pinto's make 140 ish on these rollers with 40's but they too benifit from 45's to increase the rev range and thus the top end power.

 

Hilgie that was my aim to prove that you could use 40's but the set i had didn't make the beans. I have no axe to grind with the use of carbs I just had the chance to do this test while I overhaul my 45's.

 

If I can get hold of a set I will try and repeat the test with 34mm chokes and I will repeat it once again with 45's and 36mm chokes.

I will post the results as always.

[PumaRacing 1]

I mean that a set of 40s can't possibly knock 8 bhp OFF a 1.9 8v unless there's something seriously wrong with the installation or the engine. In fact they should give about 10 bhp extra if the manifold and filters are ok. 32mm chokes can cope with 140 or so bhp so that isn't the problem either. If the engine won't rev past 5500 rpm I'd look at fuel supply or for a broken valve spring.

[taffycrook 2]

The engine will rev pat 5500 but the power has long gone. On injection max power was at 6830 on the carbs max power was at 5370 and we ran it to 5770 to see if it held on but it didn't. All the basic checks were carried out ie full throttle, fuelling (using wide band O2) timing set to best possible setting.

The only thing that could effect the result that hasn't been checked is the manifold, this may have a bearing on the result as they seldom fit as well as they should and this one has not been port matched due to time constraints.

[Livelee 0]

I guess 40's on an mi16 would would be too small then? I've been given a pair of 40's. The car is track only. My question is will the midrange power increase be more of an advantage over any peak power I might lose?

[taffycrook 2]

Finaly got around to putting the 45's on this engine on the weekend.

What a difference!!!! The thing now flies all the way round to 7k and more, but it is a scrap yard lump and not a race motor so 7k is the limit.

I will try to get it on the rollers soon to see how much it has helped the power output.

No other changes have been made to the engine, so that seems to rule out a problem with the lump. Plus it has done well over 750 laps of Llandow on the 40's and only leaks a bit of oil.

Shame I never got around to finding the 34mm chokes and trying them but time waits for no man.

 

I will post the results here when it has been done.

[Richie-Van-GTi 70 2 Cars]

was it setup properly on the rollers and was it plumbed to run the ignition advance?

[taffycrook 2]

Richie which set of carbs?

 

the 40's were set up on the rollers and timing adjusted to suit.

45's just put on and driven. I will try and get them on the rollers soon.

[andy0075 9 1 Cars]

Hi,

 

what are the choke and jet sizes in your 45's compared to the one in the 40's ?

 

cheers,

Andy

[ashley peddle 3]

my car has 40 DCOM's... (also cammed)

 

would happily put it against ANY standard 1.9 8v

 

im afftraid you are actualy talking nonesence - try setting them up properly and then come back (had mine set up professionally at pete baldwins)

 

At Cadwell my 205 was just a tiny bit slower to a fully rebuilt/prooven standard mi16 on the straights

[taffycrook 2]

im afftraid you are actualy talking nonesence - try setting them up properly and then come back (had mine set up professionally at pete baldwins)

 

Ashley are you sure I am talking rubbish?

Just how many cars have you run on carbs? I have done quite a few, and am I just reporting my findings in this particlar case.

The car was set up properly on the 40's within the limits of the set up I had available. If you bother to read the whole post the car is using 32mm chokes which is what came with the carbs. It runs well has more torque than a std 1.9 but was a touch down on power. As tested on the same roling road. FACT

Now it has 45's it is much faster FACT. Did a full day at the track yesterday and with the same driver is quicker around a lap than before. It has 36mm chokes and jetted to suit. Checked on a wide band lambda.

I am sure it would of been much better if I had 34mm chokes to go in the 40's but I didn't so couldn't test this set up.

 

Still you are entitled to your opinion.

[maturin23 10]

From a logic point of view surely a better first test of your theory would have been to fit another set of 40's with identical choke size and see if there was any improvement?

[Longun 1]

Can someone please try and clear something up for me. I'm running 40's on my 1.6 with no problems and nice power. The question, is there a limit to 40's Can they only handle smaller engines or lower power?

[VisaGTi16v 1]

http://www.pumaracing.co.uk/Chokes.htm

 

If you can get a 34mm choke into a pair of 40's then in theory they are good for 159bhp although im sure I read somewhere that another bit of them becomes the limiting factor before then so you couldnt get that much

[daza4 24]

Well I have read the whole thread and thank you for the feedback. Its always usefull to do this.

 

I have just fitted 45's to my car due to my thinking that they are technically downtuned to run my standard engine but for my future plans ie headwork and different cam they will be then able to cope with more tuning as I go. I did do a bit of research into this and it seemed the 40's work well on a 1.6 and the 45's better on the 1.9's.

 

As it has been said early on this thread these carbs where just put on to test. Tests were carried out and the results have been published. then the comments fly in.

 

Read the whole article carefully.

 

There are also lots of threads arguing this same point but fair play "taffycrook" actually tried with the equipment he had to see what happened.

 

Well done and thanks for sharing it with us.

[maturin23 10]

I think the point some people were making was that is was incorrect to suggest that the results of his 'test' were proof (partial at least) that 40's were under-specced for 1.9s. Putting a set of 45s and getting more power as a result was used as further proof.

 

I think people are merely suggesting there may be more to the results than the carb size - and that a single-sample non-scientific 'test' shouldn't be held up as proof of anything!

Edited April 13, 2007 by maturin23

[Hilgie 16 2 Cars]

@taffy: I think the jetting of your 40s carbs was just plain wrong.

 

Mine had 145bhp on the rollers, was setup great and flew to 6750 without hesitation.

 

Now you've put 45s on just proves one thing: they have the right jetting for this engine.

[ashley peddle 3]

Still you are entitled to your opinion.

 

Yup i am

 

would love to stick my 1.9 on the same rollers that you have used to see the result

[taffycrook 2]

I would welcome it myself.

I have been using these rollers for years and they give very repeatable results. Too repeatable as the expected power is often not found when testing different set ups.

 

Stripped the 40's down as they were to be used on another car and I found the chokes to be 34mm. Nothing wrong with them either.

The fuelling was set up on the rollers using a wide band lambda and very little was gained from the slight changes made from the best guess set up I used to start with.

Should have the results from the 45's this week these have not been set up but used a best guess set up i use for similar engines.

Seeing that the 40's were 34mm and not the 32mm marked on the chokes I am not expecting huge gains in power but the extra torque might prove useful.

Lap times are around a sec a lap quicker and the whole thing feels less strangled in the upper rpm.

Proof of the pudding will be in the results from the dyno.

I will as always post the results good bad or indifferent.

[taffycrook 2]

Doc1.docThe results are in.

 

129bhp 130lbs/ft.

 

I have put them on a graph to show the difference.

At the wheels the 45's are some 9bhp up but once corrected they are only 4bhp better. But look how much better they are in the upper rev range.

They lose out a bit low down but come into there own further up.

Edited April 18, 2007 by taffycrook

[petert 554]

Well done. It's good to see others publishing well researched and nicely presented research. The 40's definitely strangle it a bit up the top.

[Longun 1]

Yea there is something weird going on there. Here is a graph of my 1.6 on 40's different rr but the power is high up the rev range like yours on 45's. Nice comparison but something must be wrong somewhere with the 40 setup as they can do more.

 

http://www.205gti.me.uk/205/rr/power.jpg