Manta B 2.0E Cih Efi To Weber Dcoe Conversion

[opelmantagsi]

I am keeping my 2.0 CIH engine, dont want to do a 16v conversion on this car, just looking for advise on ditching the bosch LE system which is causing problems electrically and going with twin weber dcoe carbs

my car is right hand drive

[spiney_norman]

Fairly straight forward as far as I know, but you'd need to move the servo/master cylinder as it'll foul the carbs. Also, I'm pretty sure the original injection fuel pump would put out too great a pressure for carbs.

[lamchop77]

I am keeping my 2.0 CIH engine, dont want to do a 16v conversion on this car, just looking for advise on ditching the bosch LE system which is causing problems electrically and going with twin weber dcoe carbs

my car is right hand drive

Fairly easy to do, literally unplug the injection system at the bulkhead and remove the wiring as it is a separate loom. I would not use the pump at the rear as it will pressure up too much. Ditch it completely and replace with a red top facet pump and a Filter King filter with adjustable pressure reg on. You will only need one line to the pump from the tank. The Facet pump is an on demand pump so its all dead simple.

The servo does need moving or replacing with a VW polo one (i think...can anyone confirm?). If you move the servo you position it where the airbox would sit and make up a tube and rod to go from the bulkhead to the rear of the servo. This gives you just enough room for pancake style filters.

If your fitting 40's are you upping the cam? If you aren't you won't really gain anything but you will increase the fuel consumption drastically. Other optio is to get an earlier manta twin choke manifold and fit a 38 DGAS. Bit better fuel economy and will still perform well plus you won't need to move anything.

HTH

Chris

[Rick-Manta]

You'd need to change the camshaft anyway, the overlap for injected and carb'd engines are different for some reason I don't fully understand, witchcraft I think! This shouldn't be difficult as you'd just buy a camshaft kit as if you were buying one for an earlier carb'd CIH manta, they'll probably be cheaper than the GTE ones too.

[rutts]

you dont need to change cam it will work no problem

[Rick-Manta]

^ It'll work, if a poorly setup engine is what you want.

[lamchop77]

^ It'll work, if a poorly setup engine is what you want.

Poorly set up engine???

Difference between a 2.0s and a 2.0e cam

Timings for a 2.0s

32 90 72 50

Timings for a 2.0e

34 88 74 48

The lobe centre angle, duration and lift are all the same, the only differences are the timing figures which are extremely small, and the fact that the 2.os cam is retarded by 9 degrees whereas the gte is retarded by 7 degrees. If you skim the head you can cause that much of a difference. For that sort of change you will not notice a difference on a std motor.

HTH

Chris

Edited November 2, 2010 by lamchop77

[Rick-Manta]

Well those timing figures are closer than I expected yes but you've missed the point. If you skim the head all the valve figures will drop. It's the overlap that's needed for carbs, the difference in those numbers you've kindly posted will stay the same no matter how much you skim or shim. I assumed I would be talking to people who have a higher understanding of mechanical design than me why I only explained it as 'witchcraft', but as is the case I'll have to explain since I am being questioned:-

Carbs rely on a certain level of vacuum to deliver fuel through the jets and this is created by the valve overlap, ie when both valves are open the exhaust leaving the chamber creates a depression in the inlet port meaning a higher vacuum pressure is created and supplies fuel to the correct requirement dictated by the engine. Injection systems are already higher pressure, hence the earlier advise on changing the fuel pump and fuel delivery is controlled by the system and not the physics of the engine, meaning the overlap isn't required and will be more effiecient without it. Now, by not having a camshaft designed for carbs doesn't mean the vacuum disappears altogether as the induction stroke of each cylinder creates it and the engine on carbs should run, but will never be right so please trust me when I say it will have more flat spots than Holland!! Yes, a poorly setup engine like I say!

Anyone else??

Edited November 2, 2010 by Rick-Manta

[mark morris]

When i did it years ago i used a set of Torque Developments downdraught dellortos and manifolds, ran of the gte pump as advised by them, with a t piece to pressure regulator to carbs. Just connected the flow in and out of the bay with the t piece and off the to fuel reg.

I sent the dizzy to them to get it altered to suit the carbs too.

Sounded gorgeous.

Mark

[opelmantagsi]

I was hoping to use weber 45's, dont have a problem changing the cam or getting the original reground, I have a guy here in NZ thats done some work on a chevette we have worked on.

I was worried about the brake master cylinder fouling and hope that this can be overcome

Fuel is pretty cheap in NZ compared to the UK (about half the UK price) and the car wont be a daily driver so not too worried about the fuel consumption issue.

I have had fuel pump problems and have fitted an adjustable pressure regulator and guage in place of the standard regulaotr as part of my fault finding.

I want to get rid of the fuel filter from the rear axle and get that up into the engine bay where its easy to change, very interested to know more about that side of things

I have e-mailed dbilas dynamic regarding the inlet manifold and they came back asking for pictures of the engine bay which is encouraging.

The 2.0E engine in the car wil be stripped and rebuilt so can make whatever changes to valves, valve srpings, cam etc during the rebuild.

Keep the ideas coming

cheers

Derek

[mantadoc]

If you move the servo you position it where the airbox would sit and make up a tube and rod to go from the bulkhead to the rear of the servo.

Funny how we have cars with a steering column at 45 degrees designed to collapse and then mount a spear behind the headlight all the way to the bulkhead at chest height

Not a criticism, an observation.

[opelmantagsi]

kind of nervous about moving the servo at all, would be happy to convert to something else but not a dramatic departure from whats there.

cant use a pedal box mounted brake servo, thats not allowed here in NZ for road cars.

not keen on too much round my legs or anything that could impale me in an accident either.

Edited November 2, 2010 by opelmantagsi

[mantadoc]

Carbs rely on a certain level of vacuum to deliver fuel through the jets

True

and this is created by the valve overlap, ie when both valves are open the exhaust leaving the chamber creates a depression in the inlet port meaning a higher vacuum pressure is created and supplies fuel to the correct requirement dictated by the engine.

Nope. The Xmm of lift times the circumference to give the area of the valves to give the effective opening at lift has no where near the capacity to move air as does the movement of the piston down hill to create the actual depression which draws mixture in during theinduction stroke.

While scavenging of the cylinder through exhaust ports can be done this is usually more due to the length of the exhaust primaries.

The REAL reason for overlap is because large durations allow for more mixture to enter the cylinder, maximising the time at maximum lift, you have to move the constant velocity ramp section of the profile forward to do this.

Actually a lot of overlap can mean mixture is lost to the exhaust port befor it closes. However, this seems to have beneficial effect on occasion by cooling the exhaust valves taking the engine back from detonation and allowing cooler cylinder temo and a denser charge / higher compression.

However, this is typically why large overlap cams fall foul of hydro carbon emissions.

To mitigate this valve seats can be set at different heights in the head to hinder the inlet passing mixture straight out of the exhaust.

It's far more likely that the different cam profile on the GTE is due to the plenum runners shape as opposed to the normal carb manifold shape.

Or I just made it up and it is magic after all.

kind of nervous about moving the servo at all, would be happy to convert to something else but not a dramatic departure from whats there.

cant use a pedal box mounted brake servo, thats not allowed here in NZ for road cars.

not keen on too much round my legs or anything that could impale me in an accident either.

I've seen Kadetts and Chevetes where people mount a verticle master cylinder Same arrangement you basically have now shifted through 90 degrees

[rutts]

not getting into this arguement again with the higher educated guys, i am just a thicko that ran a gte cam (as recommended) with twin forties, flowed head in a 1.8 to produce 118bhp at wheels, but then again even thicko dave walker from CCC mag and emerald ECUs said the gte cam was the best cam for fast road applications with twin forty or fortyfives but what does he know .

[opelmantagsi]

how did you go with the brake servo / master cylinder?

[mantadoc]

not getting into this arguement again with the higher educated guys, i am just a thicko that ran a gte cam (as recommended) with twin forties, flowed head in a 1.8 to produce 118bhp at wheels, but then again even thicko dave walker from CCC mag and emerald ECUs said the gte cam was the best cam for fast road applications with twin forty or fortyfives but what does he know .

Seeing as nothing I've said contradicts that you wouldn't be arguing with me anyway.

Was that an Astra / Kadett GTE or similar cam in a 1.8? Just curious.

[Rick-Manta]

I'm glad that clears it up, you can use a camshaft designed for fuel injection with a carb setup after all, because Dave said so.

Edited November 3, 2010 by Rick-Manta

[opel2000]

I've known the Servo to be relieved of a bit of material before now and a piece welded into the recess in order to clear Carbs.

[lamchop77]

Well those timing figures are closer than I expected yes but you've missed the point. If you skim the head all the valve figures will drop. It's the overlap that's needed for carbs, the difference in those numbers you've kindly posted will stay the same no matter how much you skim or shim. I assumed I would be talking to people who have a higher understanding of mechanical design than me why I only explained it as 'witchcraft', but as is the case I'll have to explain since I am being questioned:-

Carbs rely on a certain level of vacuum to deliver fuel through the jets and this is created by the valve overlap, ie when both valves are open the exhaust leaving the chamber creates a depression in the inlet port meaning a higher vacuum pressure is created and supplies fuel to the correct requirement dictated by the engine. Injection systems are already higher pressure, hence the earlier advise on changing the fuel pump and fuel delivery is controlled by the system and not the physics of the engine, meaning the overlap isn't required and will be more effiecient without it. Now, by not having a camshaft designed for carbs doesn't mean the vacuum disappears altogether as the induction stroke of each cylinder creates it and the engine on carbs should run, but will never be right so please trust me when I say it will have more flat spots than Holland!! Yes, a poorly setup engine like I say!

Anyone else??

The overlap is mainly defined by the LSA (lobe separation angle), smaller the angle the more the overlap. With more overlap power will be made further up the rev range. No single cam will ever give perfct results all the way through the rev range. what i was trying to say was that the small variations in the valve opening and closing would probably be fine and you would hardly notice as the lift and duration are identical. Any flat spots would most prob be down to over /under fuelling through the rev range. Check out Opel gt forums and there is a list of the many cams available, look at the differences.

Another thing to note is that if you have a performance cam they don't list them as injection non injection as a rule.A rolling road tune tends to lend a hand in a situation such as this as the car is monitored under all conditions and load.

I ain't no expert just trying to help out.

Chris

[rutts]

thats the one mantadoc astra gte mk1 1.8, it was found to be best cam to use if you did not require to venture past 6500rpm bit flat upto 4000rpm though but if you keep it spinning no problem .

[mantadoc]

thats the one mantadoc astra gte mk1 1.8, it was found to be best cam to use if you did not require to venture past 6500rpm bit flat upto 4000rpm though but if you keep it spinning no problem .

It's a shame the Manta 1.8 was "strangled" for placement in the model range reasons, with the Astra GTE 115 bhp out of the box and a minor upgrade of the GTEs to Redtop the range could probably have had longer legs.

[steveopel]

You could always pick up a twin downdraft manifold and save moving the servo i was told that they were fitted to the Rekord Sprints many years ago.

[opelmantagsi]

I can possibly track down an inlet manifold off an old 1.9L Holden Sunbird, they were fitted with the 1.9L Opel CIH engine

anyone know if the manifold connections as the same as the 2.0L engine?

[rutts]

same fitting on 2.0 engine. record sprint twin manifold with carbs on german ebay £400 bargain i reckon

[opelmantagsi]

been in contact with dbilas dynamic, they say their short manifold (90mm) should do the trick

part number 01.020.026k

anyone out there tried these?