Author Topic: New member here with my slightly modified Continental GT 535  (Read 10646 times)

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Taurim

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Reply #15 on: December 25, 2020, 06:23:37 pm
Regarding the rolled entry shape of the stack, studies have found that there is less than 5% difference in actual flow berween a flat cutoff and a full 180° rolled entry. So I wouldn't worry too much about that.

I have this well known drawing from a David Vizard's book :



Maybe there is only 3% difference. But why not trying to get it ?  :)


I also have this drawing for the whole intake tract length related to RPM (with some lines added in the useful range for us) :



If I make no mistake my intake tract is now 90 + 228 + 80 = 398 mm  / 15.7 inches. That should be OK from 4500 to 6200 RPM. It's a bit high but there is not enough room in the airbox to do much better than that.

The perfect length would be 22.5 inches. That would require a 25 cm long velocity stack... that's outside of the airbox ;D
« Last Edit: December 25, 2020, 07:14:44 pm by Taurim »


derottone

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Reply #16 on: December 25, 2020, 07:08:34 pm
The length depends on the duration of the intake cam too. My calculator says with stock cams 15" should be pretty optimal.  ;)
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Taurim

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Reply #17 on: December 25, 2020, 07:22:48 pm
How did you calculate that ?

And what is the impact of the stock intake cam retarded by 1 tooth ?

It should give BTDC 25°32, ABDC 69°28 compared to stock BTDC 35°, ABDC 60°

Yes, the duration is the same  :)

Edit : Found that (from David Vizard) :

L = ((720 - ECD) x 0.25V x 2) / (RPM x RV) - 0.5D

L = total runner length
ECD = effective cam duration
V = speed of sound (ft/sec)
RV = order of wave
D = diameter of runner
« Last Edit: December 25, 2020, 07:25:40 pm by Taurim »


derottone

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Reply #18 on: December 25, 2020, 07:31:36 pm
I don't remember how my calculator works, I usually derive the formulas myself build upon the best theory I can think of and compare it to other results.

Inputs are very similar to yours, with Temperature because that changes the speed of sound.
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Taurim

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Reply #19 on: December 25, 2020, 07:49:19 pm
The problem in that equation is "effective" cam duration... which is probably mid lift, so a lot less than 275°  ???

I stop caring about that for today ;D It would be more useful for me to check the weather prediction. It's too cold and rainy to perform some road testing  :'(
« Last Edit: December 25, 2020, 07:52:01 pm by Taurim »


derottone

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Reply #20 on: December 25, 2020, 08:01:28 pm
I think I've used 250deg, with 1mm valve lift.
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Bullet Whisperer

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Reply #21 on: December 25, 2020, 08:48:24 pm
Hi Taurim,
 Interesting to see you have retarded what appears to be the std inlet cam by 1 tooth, I have done this on one CGT with performance cams fitted so far and will be doing the same with another soon. I have also used this trick on many 'cast iron' engines, with std and performance cams and a couple of AVL engines. I would expect some improvement from what you have done, however, and it would seem to be the case. Thanks for sharing this  8).
 B.W.


Taurim

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Reply #22 on: December 25, 2020, 09:01:13 pm
Hi Paul, we discussed about your latest CGT "ASBO" via Youtube and Facebook  ;)

I retarded the standard inlet cam by one tooth following your advice because as you know performance cams are unavailable at the moment... But I may have found a unused set :D

To be continued  ;)


gizzo

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Reply #23 on: December 25, 2020, 11:06:23 pm
Great work and thanks for the discussion on the trumpet. That's interesting. FWIW I've done pretty much the same mods my bike: Inlet cam retarded (per discussion with GHG), barrel skim, pcv & at200, header & muffler, ace air cleaner kit. I worked on the ports, but focussed more on removing the huge step between inlet port and insulator/injector stub. I removed a bunch of casting flashing from the exhaust port and smoothed the lot out but I don't think I enlarged the ports as much as it looks like you have. Can confirm my GT pulls harder than a stock bike and hoses a 500 UCE bullet.

I think I'll spring for cams when they become available again.
simon from south Australia
Continental GT
Pantah
Monster
DR250
DRZ400SM


oldphart

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Reply #24 on: December 25, 2020, 11:30:42 pm
Crikey. You're certainly having fun with that poor bike. Are you a compulsive modifier or will you just get it 'right' and then ride the wheels off it? It's good to see though. I like these sorts of projects. Well done.
Grandpa Slow

2019 Himalayan.


Taurim

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Reply #25 on: December 25, 2020, 11:41:38 pm
Thanks gizzo  ;)

I did not talked about that because I forgot to take some pictures but I did some work on the exhaust header also.
As you saw it the exhaust port is enlarged at 35 mm. Then I machined a ring to receive the 41 mm header tube with 35 mm ID matching the port and 28 mm long (If I remember correctly).
Then I inserted a OD 38/ID 35 tube inside the header. All of this makes a constant matched 35 mm diameter from the head to approximately the position of the original lambda sensor (I reduces the bung protrusion inside the tube as much as possible).

Once again it probably adds almost nothing performance wise but it's nice to know it is looking clean inside ;D

I read the discussion here about sleeves and anti-reversion ;)

Did your AT work well ? What target AFR did you choose ? For me this map goes now from 14 for little openings/revs to 12.8 when WOT and high RPM.
I have yet to test it but you know, it's the winter this side of the globe  :'(


gizzo

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Reply #26 on: December 26, 2020, 12:01:33 am
The AT seems to work well. I went for 13.2 across the board apart from around 3-4k at light throttle for cruising at 13.8. I ought to change it to 12.somehing for WOT but haven't yet.
I removed all the ignition advance from the map supplied for the engine with exhaust. It doesn't seem to need it since the squish mod and it doesn't ping anymore, unless you really try.
simon from south Australia
Continental GT
Pantah
Monster
DR250
DRZ400SM


Taurim

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Reply #27 on: December 26, 2020, 12:03:08 am
Crikey. You're certainly having fun with that poor bike. Are you a compulsive modifier or will you just get it 'right' and then ride the wheels off it? It's good to see though. I like these sorts of projects. Well done.

Thanks  ;)

I bought it to modify it to my taste and as a past time during Covid Crisis (this is the CGT 535 CV19 Edition !). The first phase (during first Covid confinement...) was the look and the handling and very little on the engine (PC5, filter, exhaust). I did several thousands kilometres this summer and had great fun with it, even though the engine could be better...

Now during the second confinement and the Winter I am not riding it so I started the second phase : doing all I can to improve engine performance and take the time to do it properly.

It's a lot more fun than watching TV series  ;D

After that I will have to fine tune it, maybe a Dyno measurement to known where I am and that's all. It will be exactly like I want with hopefully the performance matching the look  :)
It's not a matter of absolute performance (I just have to ride my Ducati Monster 1100 if I want more performance !) but a matter of character I want from that little thumper  :)


Taurim

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Reply #28 on: December 26, 2020, 12:10:38 am
The AT seems to work well. I went for 13.2 across the board apart from around 3-4k at light throttle for cruising at 13.8. I ought to change it to 12.somehing for WOT but haven't yet.
I removed all the ignition advance from the map supplied for the engine with exhaust. It doesn't seem to need it since the squish mod and it doesn't ping anymore, unless you really try.

Tomorrow I will have to share what I put in AFR and Ignition maps so that we can discuss about it  ;) But obviously I have not enough return on how it will work !
We won't be able to compare injection and Trim maps as I have a Euro 4 bike with a very different ECU and more sensors.


gizzo

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Reply #29 on: December 26, 2020, 12:31:49 am
Tomorrow I will have to share what I put in AFR and Ignition maps so that we can discuss about it  ;) But obviously I have not enough return on how it will work !
We won't be able to compare injection and Trim maps as I have a Euro 4 bike with a very different ECU and more sensors.

Sounds good!
simon from south Australia
Continental GT
Pantah
Monster
DR250
DRZ400SM