JuhaV Posted February 18, 2005 Share Posted February 18, 2005 Hi, Reasonable or not, I have now performed some mild head porting to my Sporti. I have written a few words about that on my webpage, so if the net result proves to be less power than before, so we all know what route not to take Take a look if interested. br, JuhaV Link to comment Share on other sites More sharing options...
Skeeve Posted February 18, 2005 Share Posted February 18, 2005 Reasonable or not, I have now performed some mild head porting to my Sporti. I have written a few words about that on my webpage, so if the net result proves to be less power than before, so we all know what route not to take 43601[/snapback] "In the exhaust channels I smoothed down the step between the head and the Termignoni exhaust adapter even if not removing it completely. ." Doh! Sure wish you'd asked here before going this route: I'm certain you would have heard from several people that there's a reason for a step in the exhaust port, as it helps prevent reversion of the exhaust flow. So you might see a serious flat spot in some portion of the powerband that wasn't there before. Altho', I may be wrong: from the picture, it looks as if the step was in the roof of the exhaust port, which is counter to the normal? location of the floor of the exhaust port. So maybe you're going to come out o.k. with this change? Definitely let us know your results! Very cool stuff, love your site! Link to comment Share on other sites More sharing options...
JuhaV Posted February 18, 2005 Author Share Posted February 18, 2005 Sure wish you'd asked here before going this route: I'm certain you would have heard from several people that there's a reason for a step in the exhaust port, as it helps prevent reversion of the exhaust flow. So you might see a serious flat spot in some portion of the powerband that wasn't there before. Altho', I may be wrong: from the picture, it looks as if the step was in the roof of the exhaust port, which is counter to the normal? location of the floor of the exhaust port. So maybe you're going to come out o.k. with this change? Definitely let us know your results! 43611[/snapback] Hi Skeeve, Thanks for your input. Actually, I heard about the same thing before I dremelled my way into the exhaust channel However, my reasoning here was the following. It seemed that the step was due to the Termignoni adapter (having larger inside diameter than the channel) and if using the original pipe there would not be such a step at all ? I did not check this carefully out, but maybe someone can confirm if the standard pipes create such a step there or not. Considering that Termignoni people really know what they are doing I thought that the step might be there for purpose, but ... The step had a "height" of about 1-1.5 mm and it was symmetrical all around the channel. Now, the step is down to maybe 0.5 mm. Which way is roof ? Is it opposite side compared to the valve opening ? We will see how it goes in practise. I will report here when I get the bike running and the snow is gone from the local roads. Before doing this porting, I asked around locally a little and there seemed to be a wide variety of opinions how to perform porting in a Guzzi. Regarding the exhaust step issue, for example, there was opinion both against and favour of removing the step. I guess, I took the middle road there Learning by doing, JuhaV Link to comment Share on other sites More sharing options...
Skeeve Posted February 20, 2005 Share Posted February 20, 2005 Hi Skeeve, Thanks for your input. Actually, I heard about the same thing before I dremelled my way into the exhaust channel However, my reasoning here was the following. It seemed that the step was due to the Termignoni adapter (having larger inside diameter than the channel) and if using the original pipe there would not be such a step at all ? Sorry, don't know Termignione (T-virus?) adapter... I presume that this is an aftermarket header, with a larger I.D. than the stock header? Considering that Termignoni people really know what they are doing I thought that the step might be there for purpose, but ... The step had a "height" of about 1-1.5 mm and it was symmetrical all around the channel. Now, the step is down to maybe 0.5 mm. Which way is roof ? Is it opposite side compared to the valve opening ? Seems like you hold Termignione in high regard but not high enough not to question their decisions... "Roof" or "ceiling" of the port(s) are upper interior surface, as situated with head installed for use on engine. In OHV engines, it's the surface with the valve guide; in the pictures you supplied which appear to have been taken with head placed upside-down on bench, the "roof" of the port is actually at the bottom of the picture. "Floor" of the port is the side with the valve seat (again, in an OHV engine.) Before doing this porting, I asked around locally a little and there seemed to be a wide variety of opinions how to perform porting in a Guzzi. Regarding the exhaust step issue, for example, there was opinion both against and favour of removing the step. I guess, I took the middle road there Learning by doing, JuhaV 43613[/snapback] Hey, at least you're willing to try! That takes some guts; replacement heads aren't cheap if you mess it up! I hope your attempt proves more than satisfactory! Ride on! Link to comment Share on other sites More sharing options...
JuhaV Posted February 21, 2005 Author Share Posted February 21, 2005 Seems like you hold Termignione in high regard but not high enough not to question their decisions... Yes, I really like the quality of the Termignoni exhaust system. Anyway, this is the exhaust manufacturer that provides their systems, for example, to those numerous Ducatis. Not sure if that fact directly reflects the quality, but at least it makes their systems rather pricey In this case I simply thought that the Termignoni people choose to have the larger header pipe diameter (creating that step) instead of a smoother joint with the exhaust port (smaller diameter header, but no step). Because they did not have the possibility to change the exhaust port diameter in the head, so they went the less restrictive route of the two possible choices available. By the way, I finally checked out the original Sporti header and it has the same inside diameter than the exhaust port. Therefore, it does not create any step at that location were I had the step with the Termignoni header. However, there is a signifant widening of the original tube, i.e. even a bigger "step" at about 50 mm downstream from the start of the header. Don't know if this is really because of flow considerations or simply because of manufacturing reasons. This step is about 4-5 mm in height and could really create some reverse flow prevention effects. Anyway, I can appreciate the reverse flow blocking scheme, but somehow I think (by intuition ) that that step would need to be somewhat farther away from the exhaust valve to have a real effect. The one in the original header could have some effect. Maybe someone can shine some more light into this ? Because of its pulsing, non-steady nature it seems that understanding the flow in and out of the engine is really challenging. Even a flow bench cannot simulate such a situation perfectly, because the hot combustion gases will in reality behave in a different manner than a cold steady air flow. Also, any change in the inlet system or exhaust system will change their resonance behaviour. Hey, at least you're willing to try! That takes some guts; replacement heads aren't cheap if you mess it up! I hope your attempt proves more than satisfactory! Nah, my changes there were rather minor and I am quite confident that I will not see any very significant effects. My primary aim was to get the two heads in better balance compared to each other. My thinking here is that if one makes a relatively little change in the shape of the port there where the port area/diameter is already quite large (away from the vicinity of the valves), then you propably cannot completely mess up the results. On the other hand, going closer to the area of the valves is completely another story, because there the flow is forced to go through a much narrower cap and the port and the valve shape can have very significant effects on that flow. There must be some very well performing Guzzi heads out there. Would love to hear some details how they were modified ! br, JuhaV Link to comment Share on other sites More sharing options...
gthyni Posted February 21, 2005 Share Posted February 21, 2005 Nice Juha, I was pondering if I would dare to get in there with the dremel myself. But since I need to pocket the valve seats a bit anyway I will let Mats at EMP do the porting work too. I'll discuss the valve bit too with him and hear what he recommend. Tuning is fun, if it just would stop snowing so I could spend some of my free time at home in the garage instead of showeling snow Link to comment Share on other sites More sharing options...
JuhaV Posted February 22, 2005 Author Share Posted February 22, 2005 I'll discuss the valve bit too with him and hear what he recommend. Let us hear what you learn from them. I am also interested to hear how are your current valve stems and valve guides doing. I was rather surprised to see that the original ones seem to be quite soft stuff and prone to wear out quite fast. In my case 33 000 km were enough to send them into the bin. br, JuhaV Link to comment Share on other sites More sharing options...
luhbo Posted February 22, 2005 Share Posted February 22, 2005 ... that there's a reason for a step in the exhaust port, as it helps prevent reversion of the exhaust flow. So you might see a serious flat spot in some portion of the powerband that wasn't there before.... 43611[/snapback] It's not necessarily unwanted to have some reversion of the exhaust flow, the opposite normaly is the case. The reason is, that while both valves are open a varying amount of fresh gas leaves the head and should be brought back just before the outlet closes. That's for 4-stroke engines nearly the same way as for the screamers. That you always have to change gains here against losses there should be the basic problem of tuning in every case. I know only one tuning item that promises gains everywhere An other possibility to deal with this step would be welding a short piece of tube to the header, so that you get a better insulation between the head and the hot exhaust flow. Hubert Link to comment Share on other sites More sharing options...
JuhaV Posted February 22, 2005 Author Share Posted February 22, 2005 I know only one tuning item that promises gains everywhere What is it then ? br, JuhaV PS. added some new pics on my site. Link to comment Share on other sites More sharing options...
DeBenGuzzi Posted February 22, 2005 Share Posted February 22, 2005 I know a super fast way to double your horsepower, and its way cheaper than porting the guzzi and boreing it out and so on. "Buy a bigger bike" but me, I might be Guzzi for life Link to comment Share on other sites More sharing options...
Skeeve Posted February 22, 2005 Share Posted February 22, 2005 I know a super fast way to double your horsepower, and its way cheaper than porting the guzzi and boreing it out and so on. "Buy a bigger bike" 44060[/snapback] Sad thing is, it doesn't even have to be bigger... :\ Que sera sera! Link to comment Share on other sites More sharing options...
gthyni Posted March 9, 2005 Share Posted March 9, 2005 small update: I removed my heads and went to EMP today. He will look for suitable better flowing stainless valves. First he thought the heads have had some mild porting before because of Luigi's handiwork (very smooth compared to most other untouched heads). The first suggestion after a quick inspection was - some porting work - 1-2 mm larger better flowing valves - a moderate pocketing (under 1 mm) He will do a closer inspection and some digging in Ferrea valve catalogues and call me back with a final suggestion and price estimation. Link to comment Share on other sites More sharing options...
JuhaV Posted March 11, 2005 Author Share Posted March 11, 2005 > some porting work Please, if possible ask them about that exhaust side "step" we have been discussing above. > 1-2 mm larger better flowing valves Ok, this will increase top end but what happens to the low end ? Bigger valves mean slower flow velocities, which could mean poorer mixing and/or less effective filling due to the lack of inlet charge momentum ? In order to do this, they need to change the valve seats. Yes ? > a moderate pocketing (under 1 mm) Is this simply embedding the valves deeper into the heads/seats ? Seems that it will decrease the flow but you may need it because more aggressive/higher lifting cam ? Keep your digicamera without if possible A couple of weeks to go and I will try to fire up the Sport first time with the new pistons and head work. It will be interesting ... br, JuhaV Link to comment Share on other sites More sharing options...
gthyni Posted March 11, 2005 Share Posted March 11, 2005 >> some porting work > Please, if possible ask them about that exhaust side "step" we have been discussing above. Will try to remember that, next time I see him. >> 1-2 mm larger better flowing valves >Ok, this will increase top end but what happens to the low end ? Bigger valves mean slower flow >velocities, which could mean poorer mixing and/or less effective filling due to the lack of inlet >charge momentum ? Yes, it is always a compromise. Pocketing reduce the flow a bit, to compensate for that better flowing a-little-larger valves is an option. I trust my 1064cc still gives me all the power I need through the whole register. An R6 put out 100+ hp from 600 cc and is still driveable. > In order to do this, they need to change the valve seats. Yes ? Yes but it needs to be done for pocketing anyway. >> a moderate pocketing (under 1 mm) >Is this simply embedding the valves deeper into the heads/seats ? Seems that it will decrease the >flow but you may need it because more aggressive/higher lifting cam ? Yes, I have a aggresive camshft to try if I get all the other parts together. Mats was asking me about the new pistons since aggressive cams make you loose a bit compression. A got a pair of FBF pistons which will go in this weekend I hope to make up for that. > Keep your digicamera without if possible I will not be able to follow his work in person but the results will be posted here. > A couple of weeks to go and I will try to fire up the Sport first time with the new pistons and head > work. It will be interesting ... I estimate about a month from now, weather permitting, it is still freezing cold here up north. I start to get exaited too, I think the first trip will go to a dynocenter to get the FI dialed in. BTW: We (some guys from Luleå) were discussing rent the Virtasalmi race track a couple of weekdays (cheaper than a weekend) in August, maybe you and some friends would like to get together with us and share the cost. Link to comment Share on other sites More sharing options...
JuhaV Posted March 11, 2005 Author Share Posted March 11, 2005 We (some guys from Luleå) were discussing rent the Virtasalmi race track a couple of weekdays (cheaper than a weekend) in August, maybe you and some friends would like to get together with us and share the cost. 45931[/snapback] Yep, I am interested. Virtasalmi Motopark is a real nice track with altitude differences that make it a lively run. You can do 220-230 km/h real speed on the back straight of that track with a Guzzi. Guess how I know that Send info when you know the dates when this session could take place. BTW, there are free practise days when you pay 45 euros per bike and can drive as long as you like. br, JuhaV Link to comment Share on other sites More sharing options...
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