ChiTownSS

I'm thinking about the 224/224 thunder cam or 227/224 thunder cam. My question is, 112 lsa or 114 lsa? I DO want it to be lopey (leaning towards 112), but isn't a 112 more difficult to have tuned (meaning, surging at stops)than a 114lsa? Also, which cam (the 112 or 114) would I have to rev higher to get peak numbers?

Car specs: M6, FLP's, GMMG, Ported T.B., FIPK, & suspension mods.

Thanks in advance.

<small>[ February 16, 2003, 04:56 PM: Message edited by: ChiTownSS ]</small>

RunNE1

iTrader: (1)

I am not an expert, but it seems most M6's go with the 112 or less LSA and A4's go with the 114 LSA. It has to do with how wide the powerband is. The 114 has a wider powerband, making it ideal for A4's (only 4 gears). Whereas M6's can use a 112 or less LSA because your are in each gear for a shorter period of time. Also, if I am not wrong, the more overlap you have the higher the power shifts up in the powerband. The 114 will have a smoother idle and less surging, but with some good tuning you could make just about any cam work. I have the TR 224 224/224 .561/.561 on a 114 LSA(A4), its a great cam.

<small>[ February 16, 2003, 05:31 PM: Message edited by: RunNE1 ]</small>

ChiTownSS

So you have to wind a 114 out higher in the RPM band to get max power? And it IS a little more difficult to keep suring to a minimum in a 112?

DailyAluminumBlock

If everything else is equal (i.e. same intake centerline) the 112lsa will peak higher but also make more peak power. However, most cams including the thunder cams have 4 degrees advance ground into them. This means that the 112 lsa will have a 108 intake centerline and the 114 lsa will have a 110 intake centerline. Basically, the 112 lsa cam will be closing the intake valve two degrees sooner then the 114. Closing the intake valve earlier results in more low end power with a slight hit in high rpm power and visa versa for closing it later. Also, surging will not be that bad with either one of those cams. Hell, I have a 224/224 110lsa cam and it doesn't surge that bad although I do have ls1 edit.

98TAauto

iTrader: (2)

its hit or miss.. some cars surge and some dont. You should saw how bad mine was with the 224 114 cam in my A4 before I did a few things on edit. Still i have issues off and on. Most M6's dont have the surging issues like A4's or they arent as bad. I reccmend a 112 for ya <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

it really isnt gonna be a big difference in either a 114 or 112...

RunNE1

iTrader: (1)

It's the other way around, you have to wind out the 112 higher to get the peak power. The 112 will have more surging but tuning should take care of it.

ChiTownSS

So I would have to wind out a 112 longer to get max e.t.'s, than if I had a 114. But I will have more torque in the lower rpm's than if I had the 114? (Assuming everything is equal, except lobe sep.)

Cal

iTrader: (1)

Here's a link that sums up the LSA thing:
http://www.co.jyu.fi/~rax/lobe.htm
Note that both the 112 and the 114 LSA are considered to be a wide LSA.

DailyAluminumBlock

That is an excellent link.

However, lobe seperation angle can only be reduced so far on a fuel injected car because of the lower vacuum associated with narrowing the lsa.

Cal

iTrader: (1)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by DailyAluminumBlock:
<strong> That is an excellent link.

However, lobe seperation angle can only be reduced so far on a fuel injected car because of the lower vacuum associated with narrowing the lsa. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I'm not doubting you, but that seems backwards to me. Carburators depend on vacuum to draw the fuel into the airstream, but fuel injection forces the fuel in under presure, so it would seem to me that injected cars wouldn't care how poor the vacuum was. <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

DailyAluminumBlock

I believe the map sensor does not function correctly when you have less vacuum. My friends 68 camaro is a daily driver with a solid cam of 106 lsa and it runs great although he had manual steering and brakes.

DailyAluminumBlock

And the 68 is carburated.