caen fred Posted October 14, 2009 Share Posted October 14, 2009 This is open to all, but I think TonyD should have an idea on that matter. I run(ed) a 1972 240Z with: L28 F54 - Flat top P90 shaved 2 mm Mildly ported A fast road cam Thunderbird exhaust Dynomax cherry bomb Twice pipe 280ZX distrib crane coil Custom SU body injection with 2 GM injectors Running at 20 psi The car had enough power to follow on the track, nose in the bumper, an ex-italia champ lancia stratos during all the session Yet I wonder if a carbureted cam is what I need or if I need a injection spec. one ????? Quote Link to comment Share on other sites More sharing options...
johnc Posted October 14, 2009 Share Posted October 14, 2009 L6 engines (like most engines) like a lot of duration if the head, induction, and exhaust systems are modified. Something over 280 is good. Quote Link to comment Share on other sites More sharing options...
caen fred Posted October 14, 2009 Author Share Posted October 14, 2009 So for you the spec of a carb and FI cars are the same ? Same strong cam for both ? Thanks, Fred Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted October 14, 2009 Administrators Share Posted October 14, 2009 (edited) I am not Wiki-D, but I think I can help shed some light on this subject. Keep in mind, Fuel Injection is just another means in which to introduce fuel to the air that the engine is ingesting. Carburetors serve the same purpose. As such, the engine doesn’t care how the fuel is being fed to the air stream. When building power, regardless if the engine is carbonated or fuel injected, using the same intake manifold, exhaust etc, the cam specs for EFI and carbureted will be the same. A change in the intake manifold design would change ideal cam specs for the desired operation, but “how” the fuel is being introduced wont require a different cam spec. EFI spec, when it comes to camshafts is generally code for "Emissions compliant” and “will sometimes play well with the factory EFI tune"! You are using aftermarket EFI, as such you have full control over the fuel map and if performance is what you desire without having to meet tail pipe emissions, then stay away from cams that are specced for EFI applications because if there is a difference in the grind, it wont be in the favor of building power vs a comparable carb cam. Hope that helps, Paul Edited October 14, 2009 by BRAAP Quote Link to comment Share on other sites More sharing options...
bradyzq Posted October 15, 2009 Share Posted October 15, 2009 I run(ed) a 1972 240Z with: L28 F54 - Flat top P90 shaved 2 mm Mildly ported A fast road cam Thunderbird exhaust Dynomax cherry bomb Twice pipe 280ZX distrib crane coil Custom SU body injection with 2 GM injectors Running at 20 psi You make no mention of the turbo setup. For example, a small turbo that spools (and dies) quickly will probably not like a cam with much overlap since it is all over for the turbo before the cam wakes up. You'll just blow a fair amount of boost out the exhaust. More info needed. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted October 15, 2009 Administrators Share Posted October 15, 2009 (edited) You make no mention of the turbo setup. For example, a small turbo that spools (and dies) quickly will probably not like a cam with much overlap since it is all over for the turbo before the cam wakes up. You'll just blow a fair amount of boost out the exhaust. More info needed. I run(ed) a 1972 240Z with: L28 F54 - Flat top P90 shaved 2 mm Mildly ported A fast road cam Thunderbird exhaust Dynomax cherry bomb Twice pipe 280ZX distrib crane coil Custom SU body injection with 2 GM injectors Running at 20 psi There is NO turbo! http://forums.hybridz.org/showthread.php?t=136397 The mention of 20-PSI is the fuel pressure, not manifold AIR pressure. He is using GM throttle-body fuel injectors which typically run 11-13 PSI fuel pressure, that is now ramped up to 20 PSI and strategically hidden under the SU carb bells! caen fred's engine; Edited October 15, 2009 by BRAAP Quote Link to comment Share on other sites More sharing options...
caen fred Posted October 15, 2009 Author Share Posted October 15, 2009 Braap, I was under this impression, now it's confirmed,thanks. I think the next logical step would be Magasquirt to have the hand on the fueling. As for the fuel pressure, I picked up some HP going from 12 to 20 psi. Now I am limited by the spring of the Aeromotive regulator. I will try the beefier one to see how it goes around 22/23? Quote Link to comment Share on other sites More sharing options...
woldson Posted October 15, 2009 Share Posted October 15, 2009 carbonated.....Teehee;) Quote Link to comment Share on other sites More sharing options...
RIP260Z Posted October 15, 2009 Share Posted October 15, 2009 Caen, The subject heading is cam choice.. what is wrong with your fast cam? Do you want to change this? And if so, to what? The next logical step is to a "race cam" but I take it the engine is mainly for the road. Do you know what the specifications the fast cam you have...or am I missing something? Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 15, 2009 Share Posted October 15, 2009 I'm in line with Braap's comentary. My only caveat would be idle vacuum. With the MAP based system you have now, you will need some idle vacuum to get the requsite resolution to have an engine that will idle well while on computer control. If you go too radical, the vacuum won't be there, and idle quality will suffer. As you suggest, Megasquirt would be the next step, and it would suffer the same from lack of idle vacuum (there is a big resolution difference from 35-105kpa, as opposed to 60-105kpa, as a 'big lopey overlapped cam' might give you) But luckily, the MS comes with an Alpha-N mode, so you can tune based on throttle position and rpm...works fine on the track and with the expanded maps you have plenty of resolution for tuning drivability to and from the track. Now that you have mentioned this, I need to drop Rick Patton an e-mail. He's got 50# of my SU Carbs for about a year now (all the Datsun SU's, 65-78) so he could make up appropriate drop-in Injection Kits for all of them. I need to see where he's at on that, and see when my stuff is headed back my way. I need to put some of that stuff back onto cars! Good to see your car is working out well after the conversion Caen! Sorry I didn't drop you a line, I was at Spa again last month for the 6 Hour Oldtimer event. Maybe next year! Quote Link to comment Share on other sites More sharing options...
caen fred Posted October 15, 2009 Author Share Posted October 15, 2009 Spa, now u'r talkin... What a track One of the finest track in my all time favorite European circuits after Dijon (French Watkins Glen) and Charade. The cam is OK... but I could use more with this injection set-up I think. Can't really tell 'cause nobody have been there before That's why I share this with you guys here on the most open minded Z forum. Quote Link to comment Share on other sites More sharing options...
bradyzq Posted October 15, 2009 Share Posted October 15, 2009 Duh, brain fart. Sorry! Quote Link to comment Share on other sites More sharing options...
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