fast road cam on fuel injection

[birminghamtr7]

this is one for beans i think.

in the process of rebuilding engine bottom end is complete on wednesday, attention then turns to the head while it being done the thought of a fast road cam for a bit of extra performance appeals my car is fuel injected will the ecu take account of the extra air flow and alter injector opening times or would i need to get the ecu remapped. and what sort of performance improvement could i expect to see.

i also have fitted a four branch exhaust system,



if you factor in the earth's rotation, we are all speeding

[Beans]

Sorry, can't answer that ... yet ...
Airmetering unit should be OK, ECU might need some fettling.
Not sure about the injectors, but then they are easy to change.

<center>
<font color="blue"><i>1981 TR7 FHC Sprint (better known as 't Kreng)
1981 TR7 DHC (not very well known yet, but back on the road)
Also a 1980 TR7 DHC, 1980 TR7 DHC FI, 1981 TR7 FHC
http://tr7beans.blogspot.com/</i></font id="blue"></center>

[FI Spyder]

The oxygen sensor adjusts fuel when sensing Air/fuel mixture and is one of the inputs that determines length of time the injectors are open. If it reads that it is lean because the cam timing allows more air into combustion chamber (longer duration of intake valve being open) the ECU will hold the injector open longer. It should all be self compensating up until you get to the limit of amount of fuel the injectors can handle (which shouldn't be reached until the upper RPM range if at all.) I don't know if the mapping of the ECU would come into play at this upper limit. Some Bosch L Jetronic injection systems on some cars like some models of BMW didn't have this lambda feed back and where more dependant on the ECU mapping.

[ggreen]

I agree with FI Spyder to a degree but if this system is being fitted to a UK spec TR7 or one that is being modified I would suggest changing the injectors as they do run out of steam.

Their are a lot of good websites to work out the injector size you want for a given HP.
Try http://www.injector.com/injectorselection.php or http://www.rceng.com/technical.aspx. They even do the calculations for you !

In most cases a naturally aspirated engines will have a B.S.F.C (brake specific fuel consumption of .50. This means that an engine will consume .50 lbs of fuel per hp per hour.

The Standard injectors on a TR7 are part number 0 280 150 105 these have a flow rate of 173.6 cc @2.5 bar operating pressure or 16.53lbs/hr, but injectors max out at 80% duty cycle - this is the accepted industry standard. So for the calculation; -

16.53 x 80% divided by 50 BSFC = 26.4 bhp per cylinder.
26.4 bhp x 4cyl = 105.6 bhp

This suggests that these injectors are good for 105.6bhp in an engine that is only producing 89 bhp in USA spec. If you are fitting any go faster bits to a UK TR7 with PI the full gains will not be realised. The other draw back with these injectors is that their are a limited number of "barbed injectors" to choose from and you also need to get the correct impedance.

I have a UK TR7 fitted with PI. I am running it with a Triumph Tune camshaft, Stage 1 head, freeflow exhaust manifold and exhaust system and conical air filter . I have changed the injectors for Bosch 0280 150 152 these flow 213cc good for 130 bhp.

If you do the calculations using the websites the airflow meter is good for aprox 140 bhp as is the throttle body.

Lambda will be a problem with the four branch. Currently I am running mine open curcuit.

[Chris Turner]

I have a set of 4 NOS standard TR7 injectors for sale, I have posted here as I think more people with injected cars will see them.

www.triumphtr.co.uk
SJW 539S TR7 sprint
1980 TR7 Premium.

[bmcecosse]

ggreen - if you are running lambda open circuit - how does your system control the mixture ? It must be running blind ? Is it not possible to simply up the fuel pressure slightly with the standard injectors ?

[ggreen]

I agree its not perfect but the car has no ill effects. That is my problem with running a 4 branch manifold. The point at which the branches finally merge is some 44 inches away from the exhaust port. The lambda's need approximately 600 degrees C to wake them up. At temperatures less than that they are open loop anyway. The factory TR7 PI lambda is mounted about 6/8 inches away from the exhaust port and gets hotter and quicker. I am not sure if mounting it 44 inches away whether would allow it to it get hot enough to work correctly. I think that is a future project. I do have a standard TR7 PI exhaust manifold I could try for a comparision.

Yes you could increase the operatiing pressue but if I remember correctly when I was researching this their are drawbacks to that method. You are probably better off going up an injector size than trying to make a smaller one work harder as injectors need to close (Dwell time) to rest and cool.

By the way the ecu is not reprogrammable it is analogue -resistors and diodes etc it is not like the more modern day mapped chips. I have only ever seen one artical which recommends changing certain resistor values within the TR7 ecu but this is only theory and has never been documented to work. I do have a spare ecu and may give it a try as a second project.

[bmcecosse]

Thanks - boy am I glad my car has good old reliable twin SUs!! All that lectronics stuff scares me witless!

[Odd]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by bmcecosse</i>

Thanks - boy am I glad my car has good old reliable twin SUs!! All that lectronics stuff scares me witless!<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

It's not that complicated actually. Google and read all about the Megasquirt - and you'll realize it's actually quite easy to go for efi complete with lambda sensors [and catcons!] for a few hundred pounds + the cost of throttle bodies [Burlen have a nice design that fits directly to the SU/ZS flange...]
And then you'd be done for good with those stone age carburettors...

[Jolyon39]

Ggreen, Would wrapping the 4 branch manifold work in retaining heat all the way down to the junction of the pipes? I have heard that wrapped pipes keep the engine bay cool and you can even touch them when running.

Just hearsay but this might help you with your oxygen sensor/lambda probe.

[frankman]

.. why not thest the Saab Bosch LH-jetronic Ecu it is the same engine the same bore and ..? and you can go for an 8V or en 16V Ecu just take one before APC - 1984 ... why no try [:o)]

Hello from Switzerland

Frank

[birminghamtr7]

Youve ot me thinking, where did you aquire / what model are they out of. BOSCH 0280 150 152

if you factor in the earth's rotation, we are all speeding

[FI Spyder]

I think the my California FI only has 80 hp slightly less than the federal carbed version. I've read they went to FI acrossed the board in '81 so one engine would meet all emissions. So they must have gone to a milder cam over the carb version even though there is no indication in the parts manual? I don't plan to alter exhaust manifold or intake for originality sake. So when I eventually upgrade to 9 to 1 pistons using ggreen's calculations I wouldn't have to change injectors even if I got a slightly wilder cam although I would be at the edge. Is that correct?

[ggreen]

Birmingham TR7 I got my injectors new off e bay :-

Part No: 0 280 150 152

Applications:

Alfa 75 1.8 Turbo Essence, 1.8 Turbo IE

BMW 528 i E12

BMW 628 CSi E24

BMW 728i E23

BMW M 535i E12

FI spyder - if your engine is not going to produce in access of 105 bhp then the standard injectors should be ok if in good condition. In which case your orginal statement should apply.

[FI Spyder]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by ggreen</i>



Lambda will be a problem with the four branch. Currently I am running mine open curcuit.




<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

I've read that open circuit TR7's run rich when cold with resultant stumble. Do you have that problem?