Go to Ultimatecarpage.com

Go Back   Ultimatecarpage.com forums > Automotive forums > Technical forums


Reply
 
Thread Tools Display Modes
  #31  
Old 02-27-2008, 03:40 PM
hightower99's Avatar
hightower99 hightower99 is offline
Enthusiast
 
Join Date: Dec 2005
Posts: 1,200
Quote:
Originally Posted by revetec View Post
Sorry to burst your bubble, but there is a patent on this design already. I sighted it when I applied for my patent.

Cheers
I figured about as much (another reason why I didn't give it a serious go).

Anyways out of curiousity, what exactly did you sight when you applied for patent?

Is it the rimmed duallobe? (sounds abit dirty doesn't it... Kinda like Wankel )
__________________
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.
Reply With Quote
  #32  
Old 02-27-2008, 03:43 PM
Kozy Kozy is offline
Novice
 
Join Date: Feb 2008
Posts: 75
UK
Rimmed duallobe... lol! I like it, might get one for the missus...
Reply With Quote
  #33  
Old 02-27-2008, 03:52 PM
revetec's Avatar
revetec revetec is offline
Member
 
Join Date: Nov 2005
Posts: 581
Gold Coast, Australia
Some diesels are around the square (bore to stroke) and have little problem.
BMW are using in their new diesels (84mm bore and 90mm stroke) which isn't that under square.
High compression ratio really becomes a problem on really short stroke engines, due to the need to get the piston out of the way to allow the valves to open.
F1 have around 11:1 with a 40mm stroke. I know by my designing that this is about the maximum limit. Below 40mm you cannot get the piston to valve clearance, and if you go over 11:1 you are limited by valve angle, ie. above 11:1 with a 40mm stroke, the valves have to start going to a verticle movement and the flow of the ports and chamber shape suffers.

I know that most diesels have almost verticle valves and mostly have a chamber for the injector to operate properly. So in a larger bore engine the piston to head clearance is an issue, which limits compression ratio. At this point reducing the bore while maintaining the same piston to head clearance raises the compression ratio. The sacrifice is the shape and angle of the port, although turbos make it less of an issue.

Last edited by revetec; 02-27-2008 at 04:06 PM.
Reply With Quote
  #34  
Old 02-27-2008, 03:56 PM
revetec's Avatar
revetec revetec is offline
Member
 
Join Date: Nov 2005
Posts: 581
Gold Coast, Australia
I sighted a dual lobe cam in a figure 8 type shape with a rim on the side to retain it. The patent also had a variations of a 90deg X with 4 pistons held together with cables from one piston to another at 90degrees and a dual counter rotating twin lobed variant. I will try and locate the patent number for you.

BTW. there are over 300 patents on cam engines which I sighted prior to my application, two of them now are ours.
Reply With Quote
  #35  
Old 02-27-2008, 04:02 PM
hightower99's Avatar
hightower99 hightower99 is offline
Enthusiast
 
Join Date: Dec 2005
Posts: 1,200
Quote:
Originally Posted by revetec View Post
Some diesels are around the square (bore to stroke) and have little problem.
BMW are using in their new diesels (84mm bore and 90mm stroke) which isn't that under square.
I never said that diesel engines have to be or are all severly under square. I said that it is easier to achieve the high compression ratios (over 20:1) that they need if they maintain a relatively undersquare design.


Quote:
Originally Posted by revetec
High compression ratio really becomes a problem on really short stroke engines, due to the need to get the piston out of the way to allow the valves to open.
F1 have around 11:1 with a 40mm stroke. I know by my designing that this is about the maximum limit. Below 40mm you cannot get the piston to valve clearance, and if you go over 11:1 you are limited by valve angle, ie. above 11:1 with a 40mm stroke, the valves have to start going to a verticle movement and the flow of the ports and chamber shape suffers.
Exactly and modern diesels are running over 20:1 CRs and they normally have valve angles close to 0deg (or 180deg if you prefer) the combustion chamber is normally part of the piston (which is an effective way of "reducing" the effective bore at TDC) and the flow through the ports is compromised (one of the reasons Diesels require Turbos and have problems producing high RPM power).
__________________
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.
Reply With Quote
  #36  
Old 02-27-2008, 07:17 PM
revetec's Avatar
revetec revetec is offline
Member
 
Join Date: Nov 2005
Posts: 581
Gold Coast, Australia
My understanding is that Diesels don't rev as high because of the combustion physics of the fuel. It simply takes longer to vaporise, plus with the added weight needed for dealing with higher pressures, increases reciprocating mass.

Last edited by revetec; 02-27-2008 at 07:20 PM.
Reply With Quote
  #37  
Old 02-28-2008, 01:46 AM
hightower99's Avatar
hightower99 hightower99 is offline
Enthusiast
 
Join Date: Dec 2005
Posts: 1,200
The upper rev limit of diesel engines is held back by piston speed. Diesel engines are designed to work with constant pressure combustion (as opposed to constant volume combustion). This fact combined with the relatively low flame front speed of diesel leads to a maximum piston speed significantly lower than petrol engines. They are also strangled at higher RPM by poor port shape which again holds back maximum piston speed. Because the maximum piston speed is set and because diesel engines are made with relatively long strokes they can not achieve high RPM operation.

I have seen a model diesel engine that was able to rev past 10000RPM but that is because it had a stroke of only 10mm and was carburetted (meaning it was running closer to constant volume combustion then constant pressure).
__________________
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.
Reply With Quote
  #38  
Old 02-28-2008, 02:42 PM
revetec's Avatar
revetec revetec is offline
Member
 
Join Date: Nov 2005
Posts: 581
Gold Coast, Australia
I'll first state that Diesel really isn't my area of expertise, even though I have some knowledge in this area.

I don't think that a constant higher pressure would be a major hindrance to high RPMs, although I haven't given it enough thought and research.

This would be a good topic to research and discuss in great detail.

What is the benefit of a carburetted Diesel other than getting manifold vacuum for the brake booster and/or compression braking which is usually on the exhaust? I'll go do a google search....

Last edited by revetec; 02-28-2008 at 02:51 PM.
Reply With Quote
  #39  
Old 02-29-2008, 12:43 AM
hightower99's Avatar
hightower99 hightower99 is offline
Enthusiast
 
Join Date: Dec 2005
Posts: 1,200
Quote:
Originally Posted by revetec View Post
I don't think that a constant higher pressure would be a major hindrance to high RPMs, although I haven't given it enough thought and research.
It isn't directly the higher pressure over more of the stroke that is the problem. The problem is that because it is constant pressure combustion The flame speed becomes more of a limiting factor. During a constant volume combustion the fuel burns quickly around TDC and then the resulting hot gasses are expanded. The gasses expand much faster than the flame front speed so for petrol engines flame front speed is only an issue around TDC. With constant pressure combustion, fuel burns during most of the power stroke, meaning that the piston must travel slower than the nominal flame speed to extract work.



Quote:
Originally Posted by revetec
What is the benefit of a carburetted Diesel other than getting manifold vacuum for the brake booster and/or compression braking which is usually on the exhaust? I'll go do a google search....
Relax there is no advantage at all. Remember I said it was a small model diesel engine. The engine is only roughly 1cc and it was carburetted because it is easier to make a tiny carburettor then a tiny fuel injector for direct fuel injection. The engine could not be easily throttled and when he did change the speed he used a combination of changing the CR and opening or closing the fuel needle in the carb. I just mentioned it to show that RPM has to do with piston speed and flame front speed in a diesel.
__________________
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.
Reply With Quote
  #40  
Old 03-02-2008, 03:15 PM
revetec's Avatar
revetec revetec is offline
Member
 
Join Date: Nov 2005
Posts: 581
Gold Coast, Australia
As a note: I drove my Mercedes Vito Van (diesel) on the weekend, and it revs to about 6,000rpm

Last edited by revetec; 03-02-2008 at 03:20 PM.
Reply With Quote
  #41  
Old 03-02-2008, 04:16 PM
hightower99's Avatar
hightower99 hightower99 is offline
Enthusiast
 
Join Date: Dec 2005
Posts: 1,200
Quote:
Originally Posted by revetec View Post
As a note: I drove my Mercedes Vito Van (diesel) on the weekend, and it revs to about 6,000rpm
Really?

What did you do to get it to rev that high?
__________________
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.
Reply With Quote
  #42  
Old 03-02-2008, 04:24 PM
revetec's Avatar
revetec revetec is offline
Member
 
Join Date: Nov 2005
Posts: 581
Gold Coast, Australia
Selected 1st gear and gave it full throttle.

I think my tacho goes to 7,000rpm and redlines at 6,500rpm.

This is not mine, just an image I found on the web of a LHD cluster.


Mercedes Vito Van Instrument Cluster

Last edited by revetec; 03-02-2008 at 04:34 PM.
Reply With Quote
  #43  
Old 03-02-2008, 04:41 PM
hightower99's Avatar
hightower99 hightower99 is offline
Enthusiast
 
Join Date: Dec 2005
Posts: 1,200
Which engine does yours have?

all the engines in the Vito peak at 3800RPM...

That means that you are somehow able to rev it 2200RPM past peak HP?

Sounds alittle unbelievable to me.
__________________
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.
Reply With Quote
  #44  
Old 03-02-2008, 04:56 PM
revetec's Avatar
revetec revetec is offline
Member
 
Join Date: Nov 2005
Posts: 581
Gold Coast, Australia
Maximum power is at 3,800rpm but it revs way past that. Did you look at the tacho? I'll try and get a picture of mine tonight.
Reply With Quote
  #45  
Old 03-02-2008, 05:02 PM
hightower99's Avatar
hightower99 hightower99 is offline
Enthusiast
 
Join Date: Dec 2005
Posts: 1,200
Quote:
Originally Posted by revetec View Post
Maximum power is at 3,800rpm but it revs way past that. Did you look at the tacho? I'll try and get a picture of mine tonight.
Preferrably while achieving 6000RPM+

That has got to be one of the highest revving diesels used in a car...
__________________
Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
Engine torque is an illusion.
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT -7. The time now is 02:44 AM.

 

1998 - 2014 Ultimatecarpage.com