Gary Kemp 's 107 high lift cam

[pan]

Hello Everyone,

Does anyone know about the performance of Gary Kemp's 107 high lift cams with 104  cam pulleys in SE/s4/s4s? 

I learned from some forums that 104 cam is not recommended for turbo engine on both intake and exhaust sides because of the 272 degrees overlap and it hurts low end torque and is difficult to build up boost, so better go for Gary Kemp's 107 high lift cam.

Will it still lose some low end torque with Gary Kemp's 107 high lift cams with 104  cam pulleys? and how is the performance comparing with the stock setting?

thanks

Pan

 

[TAR]

I would contact him and ask. He is known for weel built engines.

https://lotusengineparts.com/

 

[MrDangerUS]

22 hours ago, pan said:

Hello Everyone,

Does anyone know about the performance of Gary Kemp's 107 high lift cams with 104  cam pulleys in SE/s4/s4s? 

I learned from some forums that 104 cam is not recommended for turbo engine on both intake and exhaust sides because of the 272 degrees overlap and it hurts low end torque and is difficult to build up boost, so better go for Gary Kemp's 107 high lift cam.

Will it still lose some low end torque with Gary Kemp's 107 high lift cams with 104  cam pulleys? and how is the performance comparing with the stock setting?

thanks

Pan

 

Pan,

Usually "104" high lift cam is used on the intake only. The exhaust retains "107" cam (252°  duration).

Your base line is a pair of 107/107 cams timed at 104° MOP/104° MOP, which gives your engine 44° overlap, 104° SLA and 0° intake cam center line advance.

If you install "104" cam on the intake, the combo of 104/107 cams timed at 104° MOP/104° MOP will give you  54° overlap, 104°  SLA and 0° int. cam advance.

Increasing overlap on the turbo engine contradicts boost building, therefore is not desirable.

To counter the overlap increase would require changing the cam timing (vernier pulleys required0, which will affect emissions.

The same104 int /107 exh cam combo set at 106° MOP intake/110° MOP exhaust, will reduce overlap to 46° , improve SLA to 108° and advance intake cam center line by +2°.

Timing the exhaust cam to 110 MOP does reduce the overlap, and turbo engines don't thrive on a lot of overlap like naturally aspirated engines do. It's hard to built boost in the cylinder while the exhaust valve is still open, so minimizing overlap by limiting exhaust open time helps the turbo build charge pressure in the cylinder. The downside is that opening the exhaust valve early reduces the working length of the power stroke, extracts less energy from the combustion gases, results in lower efficiency, and dumps more un-burned fuel into the exhaust (higher HC emissions). You gain more power due turbo-packing more air-fuel mix into the cylinder than you lose by opening the exhaust early. The 'More Turbo Power' aspect of the 910 engine may like running the exhaust at 110 MOP, but it's not a freebie. You pay for it.

While turbocharged engines don't thrive on more overlap, more intake duration can be beneficial at higher rpm, just like in a naturally aspirated engine. Putting a 104 cam on the intake not only will help make more top end power; but as with a naturally aspirated engine, it will cost a little low end power. If you enjoy playing in the top half of the power band, or do a lot of track days, a 104 cam on the intake can be fun.
The 104 cam net effect is similar to the S4s big valve's net effect, but for different reasons. In either case, you give up some bottom end to gain more on the top end. If you drag race a stock SE small valve and a stock S4s big valve, the SE will get off the line first and pull out an initial lead. But once the S4s gathers itself up, it will catch the SE and pull ahead for the long haul. Same net effect with the 104 hi lift cam on the intake verses the stock 107 cam. The 104 intake cam will be a little slower off the line, but will pull away over the long haul.

 

 

 

 

 

[pan]

On 11/12/2017 at 04:25, TAR said:

I would contact him and ask. He is known for weel built engines.

https://lotusengineparts.com/

 

Thank you.

i just sent him an email. Hope it would help.

[pan]

5 hours ago, MrDangerUS said:

Pan,

Usually "104" high lift cam is used on the intake only. The exhaust retains "107" cam (252°  duration).

Your base line is a pair of 107/107 cams timed at 104° MOP/104° MOP, which gives your engine 44° overlap, 104° SLA and 0° intake cam center line advance.

If you install "104" cam on the intake, the combo of 104/107 cams timed at 104° MOP/104° MOP will give you  54° overlap, 104°  SLA and 0° int. cam advance.

Increasing overlap on the turbo engine contradicts boost building, therefore is not desirable.

To counter the overlap increase would require changing the cam timing (vernier pulleys required0, which will affect emissions.

The same104 int /107 exh cam combo set at 106° MOP intake/110° MOP exhaust, will reduce overlap to 46° , improve SLA to 108° and advance intake cam center line by +2°.

Timing the exhaust cam to 110 MOP does reduce the overlap, and turbo engines don't thrive on a lot of overlap like naturally aspirated engines do. It's hard to built boost in the cylinder while the exhaust valve is still open, so minimizing overlap by limiting exhaust open time helps the turbo build charge pressure in the cylinder. The downside is that opening the exhaust valve early reduces the working length of the power stroke, extracts less energy from the combustion gases, results in lower efficiency, and dumps more un-burned fuel into the exhaust (higher HC emissions). You gain more power due turbo-packing more air-fuel mix into the cylinder than you lose by opening the exhaust early. The 'More Turbo Power' aspect of the 910 engine may like running the exhaust at 110 MOP, but it's not a freebie. You pay for it.

While turbocharged engines don't thrive on more overlap, more intake duration can be beneficial at higher rpm, just like in a naturally aspirated engine. Putting a 104 cam on the intake not only will help make more top end power; but as with a naturally aspirated engine, it will cost a little low end power. If you enjoy playing in the top half of the power band, or do a lot of track days, a 104 cam on the intake can be fun.
The 104 cam net effect is similar to the S4s big valve's net effect, but for different reasons. In either case, you give up some bottom end to gain more on the top end. If you drag race a stock SE small valve and a stock S4s big valve, the SE will get off the line first and pull out an initial lead. But once the S4s gathers itself up, it will catch the SE and pull ahead for the long haul. Same net effect with the 104 hi lift cam on the intake verses the stock 107 cam. The 104 intake cam will be a little slower off the line, but will pull away over the long haul.

 

 

 

 

 

Hello Danger,

thank you for your comment.

104 cam has higher lift and more duration than 107, I know it is not good for building up the boost, but I learnt from Dermot's website that there is a 107 high lift cam which maintains the same duration of 252 but with a higher lift just like 104. Does it help engine breathing without hurting the boost building and good for the all range torque ? And should I keep the cams timed at 100/110? or 104/104?

As you mentioned before, S4S has already had bigger valve, do I really need a high lift cam for a better breathing?

regards,

pan

[MrDangerUS]

Pan,

You wrote: but I learnt from Dermot's website that there is a 107 high lift cam which maintains the same duration of 252 but with a higher lift just like 104.

Sorry to disappoint you, but this information is not correct.

It is impossible geometrically to have 252 duration with such high lift (lobes must have a curvature to allow tappets to slide smoothly). Higher lift on Lotus cams can be achieved only by cutting into the base circle. You can not "add height" to the lobe due to the cam bearing diameter limitation.

[pan]

9 hours ago, MrDangerUS said:

Pan,

You wrote: but I learnt from Dermot's website that there is a 107 high lift cam which maintains the same duration of 252 but with a higher lift just like 104.

Sorry to disappoint you, but this information is not correct.

It is impossible geometrically to have 252 duration with such high lift (lobes must have a curvature to allow tappets to slide smoothly). Higher lift on Lotus cams can be achieved only by cutting into the base circle. You can not "add height" to the lobe due to the cam bearing diameter limitation.

Hi Danger ,

I also Learnt from the link http://espritspecial.blogspot.com/2006/08/notes-from-garry-kemp-proposed-910.html?m=1  

107 high lift cam was mentioned by Garry Kemp,

maybe it has more  lift than stock one, but not as more lift as 104, is it possible?

I am really confused about that, there is no any post talking about 107 high lift cam, does it really exist?

 

Regards

pan 

[MrDangerUS]

Pan,

The best you can do is to go straight to the source, ask Garry directly.

[drdoom]

I'd be very pleased to see anyone's account of how increased exhaust duration, by whatever means, has shown a measurable improvement to performance on any of the 90- series engines, N/A or boosted. I purchased two rather well regarded engine sim software products several years back and all indications are that:

1) - The cylinder head port/valve dimensions are over capacity except for race usage. See how valve sizes compare to Cosworth DFV, to illustrate.

2) - Though I cannot confirm via testing as yet, with inputs which are ballpark estimated with care it appears to be that the N/A motors would be better served by X MOP of 110 or greater. Intake at 104 or 106 offers best results, without question.

Steve

[naasaa]

Pan

Did you followed this further?

Lars

[drdoom]

Nothing tried and tested yet, I'm still well short of building an engine while sorting out issue after issue on the S2 restoration. I have engine simulation software for amusement from time to time but have limited work in it to normally aspirated configurations. One interesting finding came when it occurred to try the 107 type cams at 110 degree MOP. If the results can be trusted it appears that the 107 is superior to the "C" cam found in most 907 engines, comparing reasonably well at 110 MOP to 104 cam at 104 MOP's. It seems the 104 MOP has been regarded as the ultimate in cam timing, as that was the timing point of the highest spec 912 built by Lotus, the SE. I expect to confer with GK as the engine campaign nears, will relate his wisdom if offered.

Cheers 

[MrDangerUS]

Steve,

I am running "107" cams at 104° MOP intake and 106-107° MOP Exhaust, which gives me 42-41° overlap, 105-6° SLA and advances intake cam +1°. Car is running like a scalded cat.

If you set up your intake at 106° MOP and exhaust at 108°MOP, the overlap gets reduced to  38°, SLA is 107° with +1° intake cam advance

38° overlap may diminish low end performance before the onset of turbo, but would help at the higher rpm.

GK told me that 910 engine "likes" running at 105-6° int /109-110°exh MOP... smaller overlap and SLA at optimum ~108°

Edited March 21, 2020 by MrDangerUS

[drdoom]

John,

Thanks for sharing that. What is best for a Turbo engine will differ from best N/A set-up, as I see it. Turbo engine output reflects energy derived from exhaust flow in a manner differing from how X flow affects the normally aspirated, so optimal valve timing for each should differ as well, AFAIK.

Cheers