Individual Throttle Bodies, Wilder Cams!?

Hi,

A Micra expert has mentioned that by running individual throttle bodies, I have the option of using much wilder cams (for reasons he explained to me but I won't bother writing here because its quite long).

Currently, I only changed the inlet cam for a 250 deg 9mm cam, but now I am considering changing both inlet and exhaust for some bigger duration cams. The person I buy the cams off doesn't offer any more than 9mm lift.

The only concern is losing too much mid-range torque so can people with performance camshafts please chip in their views?

I don't want to 'overcam' the car., but I was thinking maybe go for 270-280 degree 9mm cams and change both inlet and exhaust?

Its a coilpack 1.4 by the way.
 

Low Rider

Poindexter
Founding Member
Moderator
Club Member
A set of '773' profile cams from Matt Humphris, which are 264deg duration and a smidge over 9mm lift. You can get away with standard valve springs and the older top biscuit shim followers on them. Power band will be 2500-7500, so a healthy spread of power and enough to pretty much max out the stock head in terms of flow.

As an alternative there's a '1601214' profile cam from Catcams which are 270deg and a bit more lift at 9.50mm but you need uprated valve springs with these as they're a tad more aggressive. I'd only recommend these if you have the later solid followers on your CGA3DE (some come with them, some don't). If you have the older type with the top biscuit shim, I'd stick with the '773' profile cams to mitigate throwing a shim and killing the engine.
 
A set of '773' profile cams from Matt Humphris, which are 264deg duration and a smidge over 9mm lift. You can get away with standard valve springs and the older top biscuit shim followers on them. Power band will be 2500-7500, so a healthy spread of power and enough to pretty much max out the stock head in terms of flow.

As an alternative there's a '1601214' profile cam from Catcams which are 270deg and a bit more lift at 9.50mm but you need uprated valve springs with these as they're a tad more aggressive. I'd only recommend these if you have the later solid followers on your CGA3DE (some come with them, some don't). If you have the older type with the top biscuit shim, I'd stick with the '773' profile cams to mitigate throwing a shim and killing the engine.

Thats a very similar spec to the Piper Ultimates which are 272deg and 9.07mm (inlet) and 9.02mm (exhaust).
I'd rather not mess around changing valve springs as my practical skill is limited - I can just about manage changing the cam.
So thanks for the info, Ill go with 774 (the new 773) or the piper ultimates.

Do you know the spec of the 774's? Matt lists them on eBay as 'an improvement over the 773' but there's no actual specs...
 

Low Rider

Poindexter
Founding Member
Moderator
Club Member
Yes, the '774' profile are the same as the Piper Ultimate profile in every respect.

I'd personally avoid the re-grinds from Piper since they will have a smaller base circle and pose an immediate issue with respect to setting the valve clearance. I'd imagine the fresh cams ground from blanks would be to a standard base circle, but I would double check this prior to ordering. Stock base circle FYI is 32mm.
 
Yes, the '774' profile are the same as the Piper Ultimate profile in every respect.

I'd personally avoid the re-grinds from Piper since they will have a smaller base circle and pose an immediate issue with respect to setting the valve clearance. I'd imagine the fresh cams ground from blanks would be to a standard base circle, but I would double check this prior to ordering. Stock base circle FYI is 32mm.

Thanks for confirming the 774 specs.
Yes I will only be considering fresh cams rather than regrinds.
Perfect thanks for the help!
 

frank

Club Member
bear in mind that duration is measured to different standards, some are @ 0 valvelift and some @ 10" thou and some @ 1mm lift,
so one suppliers 260 deg is another suppliers 290 deg depending on how it is measured.
and the difference in your current setup compared to a pair of fitted 774,s will end up costing about £100 per hp !
 
bear in mind that duration is measured to different standards, some are @ 0 valvelift and some @ 10" thou and some @ 1mm lift,
so one suppliers 260 deg is another suppliers 290 deg depending on how it is measured.
and the difference in your current setup compared to a pair of fitted 774,s will end up costing about £100 per hp !

Ah right okay, I didn't know that.

And yeah even if its a little bit of a difference, I don't mind. How much hp gain do you reckon it would be?

And I really do appreciate you looking out for my bank account!
However, it actually won't be as expensive as most would think since I am fitting them in myself and also, I have found a buyer for my current cams at £250, so that recoups half of the money back (although he could back out!). Plus when I get rid of the car in September, I will breaking it all down anyway so should be able to sell the 774's for at least £150 then. (hopefully!)
 
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frank

Club Member
have a look at dave,s data on post 71

the difference in duration at 1mm on those 3 cams, where the airflow starts to take effect
 
have a look at dave,s data on post 71

the difference in duration at 1mm on those 3 cams, where the airflow starts to take effect

Yeah I have now started to realise how the durations can be advertised without actually explaining how they are measured.
I need to scratch up on cam specs on Google, as I don't know what most of the numbers mean.
I literally just knew duration and lift, which ironically are the only numbers companies tend to advertise.

Thanks for the help!
 

frank

Club Member
going by that data ^ the kent 288 should be 60 deg more duration than stock, but at 1mm lift its only 16deg more duration, and all 4 valves are open the same amount at tdc
so the reprofiled cam is opening the valve less aggressively than the stock cam, which makes the reprofile more peaky/laggy
ideally you need an aggressively fast opening/closing cam that does,nt spit shims (valvebounce)
opening and closing faster leads to more "true" duration,
 
going by that data ^ the kent 288 should be 60 deg more duration than stock, but at 1mm lift its only 16deg more duration, and all 4 valves are open the same amount at tdc
so the reprofiled cam is opening the valve less aggressively than the stock cam, which makes the reprofile more peaky/laggy
ideally you need an aggressively fast opening/closing cam that does,nt spit shims (valvebounce)
opening and closing faster leads to more "true" duration,

I understand you now, I have just learnt something new!

The 774's have 1.80mm and 1.75mm lift at TDC, which sounds promising based on what your saying as these numbers are more greater than the Cat Cams spec, but I still have no idea what the lift at 1mm is for the 774 cams. And I have no data on my current inlet cam other than the fact it was 250deg and 9mm.

Wish I knew this stuff back then!
 
I understand you now, I have just learnt something new!

The 774's have 1.80mm and 1.75mm lift at TDC, which sounds promising based on what your saying as these numbers are more greater than the Cat Cams spec, but I still have no idea what the lift at 1mm is for the 774 cams. And I have no data on my current inlet cam other than the fact it was 250deg and 9mm.

Wish I knew this stuff back then!

I have read up on it a and finally have a much better understanding I think!

The 774's are
Timing Data Duration V/L V/C Cold F/L LATDC
Inlet Open 30 BTDC Close 62 ABDC 274 9.09mm 0.210mm 106 1.80mm
Exhaust Open 62 BBDC Close 30 ATDC 274 9.04mm 0.254mm 106 1.75mm

which I think means it takes 30deg to get to 1mm lift, then 106x2=212deg duration where the the valve is at least 1mm open, and then another 30deg to get valve from 1mm to completetly shut.

This means duration at 1mm is 272-30-30=212deg.

This is what I got from it, hope it helps the people who also didn't know. But if I am wrong, then please correct me as I don't want to give false information!

Still unsure on some of the other numbers so will need to research.

I have contacted the person I bought the 250deg 9mm inlet cam from, and asked him to give me the more detailed cam specs. So I can really compare the 774 cams to my existing setup.
 
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frank

Club Member
in theory a duration would be 180 deg, ie inlet open at bdc and closed at tdc
but in practice you need to open it btdc to help flush the gasses out of the chamber, and close abdc to cram a bit more air in while the piston is starting to return back up
so a 30/62 inlet has a 272 duration
 
in theory a duration would be 180 deg, ie inlet open at bdc and closed at tdc
but in practice you need to open it btdc to help flush the gasses out of the chamber, and close abdc to cram a bit more air in while the piston is starting to return back up
so a 30/62 inlet has a 272 duration

Ah right okay. I wasn’t sure what the 62 meant but now that all makes sense, thanks!
 
Got some more info for the cam specs of my 250 deg 9mm lift inlet cam.

Duration 250deg
Lift 9mm
[email protected] 218deg
Full Lift at 110deg
LATDC = 0.65mm

Comparing with the 774's which are:

The 774's are
Timing Data Duration V/L V/C Cold F/L LATDC
Inlet Open 30 BTDC Close 62 ABDC 274 9.09mm 0.210mm 106 1.80mm
Exhaust Open 62 BBDC Close 30 ATDC 274 9.04mm 0.254mm 106 1.75mm

[email protected] of the 774's is 242 (272-30=242 right?) and lift at TDC is almost triple!

This would suggest the 774's should give a strongish improvement right? Or am I talking nonsense?!
 
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frank

Club Member
the full lift at the lesser 106 deg has an effect on the tdc lift, so you could advance or retard either or both cams to gain or lose lift at tdc
 
the full lift at the lesser 106 deg has an effect on the tdc lift, so you could advance or retard either or both cams to gain or lose lift at tdc

Riiiiight so not much of a gain then doh!

Oh well, I better be able to sell my existing set up for good money, otherwise, as you said, this would make for a very poor 'pounds per horsepower' mod.
 

frank

Club Member
yes if you set the 773,s at 110 like these, the overlap/lift at tdc would be less eh

ASK-11-01-768x452.jpg
 
I understand what you mean, thanks as always.

And yeah I now 100% understand why the new cams wasn't the best of ideas lol!

Do you want to buy a 250deg 9mm inlet cam from me for £500?!! lool
 
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