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Search found 2256 matches

by ptuomov
Fri Sep 18, 2020 9:58 am
Forum: Engine Tech
Topic: MPFI with 16 injectors
Replies: 7
Views: 101

Re: MPFI with 16 injectors

as mentioned it is all about injector flow, fuel pressure, and pulse width. The only reason I would see to use two injectors per cylinder would be if the fuel demands of the engine were so great that at idle you could not control the idle fuel quality of the engine with one big injector, usually li...
by ptuomov
Fri Sep 18, 2020 9:46 am
Forum: Engine Tech
Topic: MPFI with 16 injectors
Replies: 7
Views: 101

Re: MPFI with 16 injectors

I've been thinking about converting my car (500ci BBM) to multi point fuel injection and having a custom intake built. The concept of having 16 injectors (2 per runner) seems quite interesting. When having 1 injector at runner end (close to valve)and the 2nd injector at runner entry what setup is t...
by ptuomov
Wed Sep 16, 2020 2:49 pm
Forum: Engine Tech
Topic: Throttle response EFI: TBI vs. MPFI on 800 hp BBC
Replies: 6
Views: 155

Re: Throttle response EFI: TBI vs. MPFI on 800 hp BBC

Simplest way to 'improve throttle response' is to use a lighter return spring. Which is a pretty good indicator that 'throttle response' is something that happens inside your head, not inside your engine. Or take out a muffler or two... As was noted earlier, your fuel system can impact throttle res...
by ptuomov
Wed Sep 16, 2020 12:26 pm
Forum: Engine Tech
Topic: Throttle response EFI: TBI vs. MPFI on 800 hp BBC
Replies: 6
Views: 155

Re: Throttle response EFI: TBI vs. MPFI on 800 hp BBC

I think the original article is mostly fake news. If I wanted a normally aspirated engine with fixed cam timing that cruises well, makes a lot of power, and transitions between the two well, then the best solution is obvious. Independent throttle bodies with throttle plates relatively close to the i...
by ptuomov
Tue Sep 15, 2020 8:05 pm
Forum: Engine Tech
Topic: Throttle response and EFI
Replies: 10
Views: 819

Re: Throttle response and EFI

I can see that the air filter etc would be time consuming to refabricate. I have no objections with a single throttle plenum EFI manifold with port injectors. That’s what I got! I was more commenting on the EFI university Holley sniper system that has eight throttles but looks like a plenum manifol...
by ptuomov
Tue Sep 15, 2020 11:17 am
Forum: Engine Tech
Topic: Throttle response and EFI
Replies: 10
Views: 819

Re: Throttle response and EFI

I can see that the air filter etc would be time consuming to refabricate. I have no objections with a single throttle plenum EFI manifold with port injectors. That’s what I got! I was more commenting on the EFI university Holley sniper system that has eight throttles but looks like a plenum manifold...
by ptuomov
Tue Sep 15, 2020 9:55 am
Forum: Engine Tech
Topic: Cam intake lobe vs exhaust lobe
Replies: 11
Views: 1479

Re: Cam intake lobe vs exhaust lobe

So the question is about the valve lift profile normalized to gave the same lift and duration? Or talking about an engine combination that happens to want the same lift and duration intake and exhaust cams, and then asking if there are any remaining differences? In a four valve DOHC engine with soli...
by ptuomov
Tue Sep 15, 2020 9:08 am
Forum: Engine Tech
Topic: Throttle response and EFI
Replies: 10
Views: 819

Re: Throttle response and EFI

Is this a plenum manifold with throttle body injection? If it’s a plenum manifold with a throttle body injection, why wouldn’t it be better to use the same number of throttles and injectors in an independent throttle body system with the throttle close to the port and injector spraying into the runn...
by ptuomov
Thu Sep 10, 2020 11:37 am
Forum: Engine Tech
Topic: Header Tube and Collector Specs "Trends"
Replies: 37
Views: 1803

Re: Header Tube and Collector Specs "Trends"

You are both partially right. Would it be possible/easy for you to quantify this, how right each of us is, using your simulator? I would suggest a single cylinder four valve turbo engine with primary/up pipe length such that the first exhaust pulse returns from the turbo close to max lift and then ...
by ptuomov
Wed Sep 09, 2020 3:54 pm
Forum: Engine Tech
Topic: Header Tube and Collector Specs "Trends"
Replies: 37
Views: 1803

Re: Header Tube and Collector Specs "Trends"

If the valve stem area forms a restriction there will be a reflection of the same sign. But it will only be a partial reflection. Its size will depend on the size of the restriction which is a function of both the cross sectional area and the flow coefficient past the valve stem. In my car, the cro...
by ptuomov
Tue Sep 08, 2020 6:32 pm
Forum: Engine Tech
Topic: Header Tube and Collector Specs "Trends"
Replies: 37
Views: 1803

Re: Header Tube and Collector Specs "Trends"

The area in the exhaust port is usually smaller than the area in the header. And a valve in the middle if the port blocking the port and forcing the wave to turn around it in all directions will make the wave see the the valve as a restriction and reflect with the same sign. See it like this, if yo...
by ptuomov
Tue Sep 08, 2020 1:57 pm
Forum: Engine Tech
Topic: Header Tube and Collector Specs "Trends"
Replies: 37
Views: 1803

Re: Header Tube and Collector Specs "Trends"

A wave changes sign against an increase in size but reflects the same against a smaller size. So both the turbine and the exhaust valve will reflect a positive wave back without changing sign. Erland I don’t believe that is the case if the exhaust valve is open. If the exhaust valve is open about 2...
by ptuomov
Tue Sep 08, 2020 11:27 am
Forum: Engine Tech
Topic: Header Tube and Collector Specs "Trends"
Replies: 37
Views: 1803

Re: Header Tube and Collector Specs "Trends"

Erland — I believe this is what happens with a single cylinder turbo engine. The high pressure wave from the blowdown gets reflected back from the turbine as a high pressure wave. This wave then makes it to the open exhaust valve (assuming typical turbo pipe lengths) as the “first coming”. The first...
by ptuomov
Sun Sep 06, 2020 12:30 pm
Forum: Engine Tech
Topic: using SF Air Turbine to determine Header problems
Replies: 31
Views: 1093

Re: using SF Air Turbine to determine Header problems

I’m running MAF sensors in my car with EFI and then lambda sensors in the exhaust. I’m thinking that both those together allow me to determine the mass air flow and fuel flow rates with sufficient accuracy. I do also have the “air turbines” aka turbos which have speed sensors, temp probes, and press...
by ptuomov
Sat Sep 05, 2020 6:35 pm
Forum: Engine Tech
Topic: Watered gas.
Replies: 17
Views: 548

Re: Watered gas.

What I’ve done 30 years ago was letting it sit and siphoning the water off from the bottom of the clear canister. This was of course before the E10 etc. The stories go that during the wars there was gasoline ethanol mix in the fuel depot. Mixing in water and letting it sit you could get diluted etha...