[Diy_efi] direct injection

Phillip Kuhn pmkls1
Fri Sep 23 02:39:52 UTC 2011

I know that this topic has gone kind of cold, but I spoke with a field engineer that came to the shop today and he had some information I thought I would share with you. When I told him about your inquiry and the information that I had been unable to obtain he also had some additional information that I was unaware of as well. He told me that the injector placement was critical and that was one of the major obstacles that took GM engineers some time to overcome. Evidently, the location of the injector in the combustion chamber and more importantly where the spray is focused is crucial to the engine performing properly. Since they were modifying existing?engine designs with the intention of making as few major modifications to the cylinder heads as possible it was quite difficult to get the injectors spraying fuel into the right part of the cylinder for the engines to run right. As a matter of fact I have replaced a cylinder head on a DI 3.6 v6
 recently.?I noticed the injector actually came in through the side of the combustion chamber ( this was probably due to the only available location to mount the injectors ) and the top of the piston and combustion chambers were very specifically shaped. They were profiled so that the fuel spray focused into a recess in the middle of the combustion chamber directly under the spark plug. I am guessing that this was to get the flame to start in the middle of the chamber and spread outward in a controlled manner. Anyhow, I thought this information was important enough to pass on. Don't get me wrong, I would love for you to successfully utilize a DI system on your project and anyone else for that matter. I just want to provide enough info so as to aid in this being completed successfully without running into so many obstacles that anyone who attempts this will not give up. I also don't want to see someone ruin a possibly rare and/or expensive cylinder head
 just to mount the injector and find out that the rest of the project is too difficult to complete. Good luck and feel free to ask anymore questions that come to mind.

From: "ScottyGrover at aol.com" <ScottyGrover at aol.com>
To: diy_efi at diy-efi.org
Sent: Friday, September 9, 2011 12:15 AM
Subject: Re: [Diy_efi] direct injection

 Thank you very much for the information.? I am designing a system for 
an air-cooled, 2.7L flat six and haven't been able to get any co-operation from 
Delphi or from my local dealer (he says I don't need to know.) 
I have studied the patents (Delphi and others) and have a good idea of the 
layout but I need the physical size (particularly the diameter) and the 
application (HP rating, engine size, and of course the part number.) 


In a message dated 9/8/2011 7:46:41 P.M. Pacific Daylight Time, 
pmkls1 at yahoo.com writes: 
I have  been a tech at GM dealerships since 2001. I don't have the slightest clue  about the other manufacturers using DI, but know a decent amount about the GM  systems. So far I haven't seen any common issues at all with the GM stuff. I  have seen a few injectors go bad and some issues with the high pressure pump  leaking fuel into the crankcase ( just like the old mechanical pumps did), but  nothing major or widespread overall. As far as the systems themselves go I  will give a detailed description of how they work etc. Currently, only the  Ecotec engines have DI versions, and all late model high feature v6 engines  (2.8, 3.0, 3.6) are DI. They all use an in-tank electric pump running at ~60  psi to send fuel up to the high pressure pump.?The high pressure  pump?is mounted on the engine, is driven off of a camshaft, and operates  exactly like the regular old mechanical fuel pumps do ( save for the pressure  output ). The entire system is a
 returnless system and
>like most newer 
  vehicles has no serviceable fuel filter. The supply pressure is regulated by 
  the ecm and a fuel pump flow control module via a pwm signal to the electric 
  in-tank pump. The fuel pressure on the high pressure side of the system is 
  also controlled by the ecm too via an actuator mounted inside the high 
  pressure pump. The system operating pressures on the high pressure side are 
  500-800 psi at idle and around 2500 psi at max output iirc. From the high 
  pressure pump forward they use heavy stainless lines with flare and ball 
  connections and are supposed to be a one-time use deal. Anytime we take a line 
  loose it is supposed to be replaced, although I have reused several without 
  any leaks. There is also a fuel rail pressure sensor located on the fuel 
  injector rail to send pressure readings back to the ecm and there is no other 
  means of testing pressure on the high pressure side. The injectors look like 
  normal injectors on the fuel rail side and
>use o-rings that appear to be 
  the same size or similar to that of regular fuel injectors( I still can't 
  figure out how the seals don't blow out at those pressures). The other end of 
  the fuel injector is very long and narrow and uses special teflon seals to 
  seal it into the cylinder head as they go directly into the combustion 
  chamber?through the intake side of the cylinder head. Special tools are 
  required to install and size the teflon seals similar to the tools used for 
  non-cut teflon seals used in transmissions. There are also special tools 
  required to remove the injectors?from the cylinder head as carbon will 
  quickly cause them to get stuck in the close-tolerance bores. Every time the 
  injectors are removed all of the seals have to be replaced. The injectors do 
  require a special high voltage driver, but I do not know the specs right now. 
  Overall, the systems operate like a regular sequential port system does and 
  are designed similar to a diesel
>system. Both fuel economy and power are 
  improved on the engines GM is using DI on currently. The latest 3.6 in the 
  base camaro is up to something like 317hp now. As far as being able to fit DI 
  to any other engine, I suppose it may be possible on some engines. Even then 
  it would require significant cylinder head modification and some fabrication. 
  You would also have to use an ECM designed for DI and be able to modify the 
  calibrations and flash the ecm which I am unsure if that is possible 
  currently. Hope this answers a few questions.
  Original Message -----
>From: Avery Nisbet <anisbet at gmail.com>
  Fred Cooke <fred.cooke at gmail.com>
>Cc: ScottyGrover at aol.com; 
  diy_efi at diy-efi.org
>Sent: Thursday, September 8, 2011 4:07 PM
  Re: [Diy_efi] direct injection
>I have heard from VAG mechanics that 
  they still have trouble with
>this. This is with the current TSFI engines 
  found in the audi's and VW
>in the US.
>Though TDI engines have been 
  around for years I only hear of them
>clogging up the EGR system not the 
  intake ports.
>I think most of this is due to EGR issues and dirty 
  air.? Where else
>would any substance that would/could coke on the 
  intake port/valve
>come from if you have DI.? The washing action of 
  Port injection
>probably helped with badly designed EGR systems in the 
>For DIY at home "testing" of DI, EGR systems could probably be 
>On Thu, Sep 8, 2011 at 1:00 PM, Fred Cooke 
  <fred.cooke at gmail.com> wrote:
>> Early examples, from at least 
  1998, perhaps earlier, are to be avoided as
>> they are usually prone to 
  coking of the intake manifolds. Very bad coking -
>> to the point of 
  blockage! The earlier cars had a lot of trouble in many
>> areas and were 
  not reliable at all. If we're talking about DI. if we're
>> talking about 
  BMW Piezo DI, I have no idea.
>> On Fri, Sep 9, 2011 at 7:18 AM, 
  Avery Nisbet <anisbet at gmail.com> wrote:
>>> A lot 
  the current car have these.
>>> GM has been using them in 
  the eco-tec(FWD 4 cylinder) engine for a
>>> while. ?Im sure 
  there a few different injector styles.
>>> The prices should come down 
  in a few years. ?You may be able to find
>>> specs by looking up 
  after market replacements.
>>> The cruze should have these 
  depending on market. ? The later model
>>> year US market cobalts 
  had them too.
>>> -Avery
>>> 2011/9/8 
  Mike <niche at iinet.net.au>:
>>> > All I know its pretty high 
  pressure, the latest bmw twin turbos use this
>>> > with piezo 
>>> > injectors that cost $2200+ (AUD) each !? But they 
  do get pretty
>>> > reasonable
>>> > fuel consumption 
>>> > around 6L/100Kms with sizable power on demand - straight 
  six 2 to 3L,
>>> > seems like the next tech step but geesh does it 
  cost !
>>> > regards
>>> > Mike
>>> > At 02:48 AM 9/9/2011, ScottyGrover at aol.com 
>>> >
>>> > Has anyone done any work on this type 
  of fuel injection? I can't get any
>>> > data from Delphi, even as 
  to the physical size (length, stem diameter.)
>>> >
  > Scotty from Hollyweird
>>> > 
>>> > Diy_efi 
  mailing list
>>> > Diy_efi at diy-efi.org
>>> > 
>>> >
  > _______________________________________________
>>> > Diy_efi 
  mailing list
>>> > Diy_efi at diy-efi.org
>>> > 
>>> >
>>> _______________________________________________
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