HomeForumsTechnical – GeneralEngineopinions on cam and tune in L98

This topic contains 6 replies, has 3 voices, and was last updated by Profile photo of dave dave 2 years, 3 months ago.

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  • #23034
    Profile photo of dave
    dave
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    Member since: March 6, 2015
    Posts: 36

    Hi,

    Have standard L98 engine with aftermarket cam in my VK with manual box. Cam specs are as follows

    .050 duration- intake 233, exhaust 237. Lobe separation angle 112. Valve lift .550.  Not sure of brand of cam as it was in the engine when I got it. Has been dyno tuned with maf sensor. Makes 380 hp at wheels. Just after peoples opinions/ experience with this engine regarding cam choice and tune. It is a bit lacking down low just off idle and sometimes pops back thru intake under acceleration from down low. Would I get much improvement going with a mafless tune? Should I change the cam? Do I need to add after market valve springs. Compression on these engines is 10.4 to 1. With a cam should get some improvement by increasing the compression also. Anyone done this?

    Dave

    #23035
    Profile photo of Heron SSV
    Heron SSV
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    Member since: May 5, 2015
    Posts: 467

    Valve springs should of been changed when the cam was done. I’d suggest getting the tune looked at, get the tuner to spend some time tuning across the whole rev range, not just up top. Cam specs sound like a mid sized cam and should go pretty good in a L98, but it’s all in the tune.

    Diff gears might also help get it off the line a bit quicker to get the revs up into the sweet spot.

    #23036
    Profile photo of cava454
    cava454
    Moderator
    Member since: February 20, 2015
    Posts: 2 203
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    Mild cam. Not much lift, so it should not making the most of the l98 heads. Power sounds right. But seems like tune needs s tweak.

    #23044
    Profile photo of dave
    dave
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    Member since: March 6, 2015
    Posts: 36

    Thanks for your responses. The gearing seems o.k. The box is a tremec TKO 600 which has shorter 1st, 2nd and 3rd gearing than the 6 speed tremecs. I know the tuner had to set the fuel ratios a bit fat to get it reasonable. I think about 13:1 from memory. Maybe just needs bit more time spent on the tuning side of things. I was thinking it may be better with a mafless tune? Originally went with the tuning done with the maf sensor for engineering and licensing.

    Dave

    #23046
    Profile photo of Heron SSV
    Heron SSV
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    Member since: May 5, 2015
    Posts: 467

    It shouldnt really matter if it runs the maf or if it is mafless, the newer LS motor mafs arent as restrictive as the old LS1 was. Definitely all in the tune, either speak to the original tuner and explain what is happening or go to a new tuner. There are heaps of threads in online forums of people who are unhappy after the get a cam fitted because of similar reasons you’ve mentioned, and a retune has sorted it out and totally transformed the car. Take Gary’s VR LSX for example, he had a shocking tune earlier in his build when the tuner mainly tuned for WOT and after taking it elsewhere it’s not a completely different animal.

    #23047
    Profile photo of Heron SSV
    Heron SSV
    Participant
    Member since: May 5, 2015
    Posts: 467

    On a side note, what type of intake are you using? I’m putting and LS3 into a VK and need to sort out the intake for engineering as it needs to be enclosed.

    #23054
    Profile photo of dave
    dave
    Participant
    Member since: March 6, 2015
    Posts: 36

    Yes same with mine for  engineering regulations, enclosed air box with a k&n filter in it. Made a filter setup on the front left side of the engine bay. Is separated from the engine bay and draws air around the headlight and past  the left side of the radiator thru the grill area. Used  100mm intake pipe and the filter is 100mm opening and about 180mm long. Was going to put some holes in under the filter for airflow from the inner wheel area but when had it dynoed he took the intake piping off to check for restriction and run it up with and without the air filter and no difference in manifold vacuum.

    Dave

    • This reply was modified 2 years, 3 months ago by Profile photo of dave dave.
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