Thoughts and help on engine upgrades.

[Behold81]

ARAF said:

You need to plot lift over time, to get a graphic representation of the ability to flow. I'm sure Behold81 knows that though, as he's always been very hands on with his car.

Valid point. You want to maximise the flow you have. So holding it in max flow longer will be a valid factor.

I'm still learning on cam specs and whilst I get what a cam does and how differences will change the characteristics I'm still working out the finer points.

I read you still want some overlap to be efficient on performance. If I have read it right the cam stevie has is little to no overlap.

[Behold81]

jameshsv said:

A nice 230/238 will do the job for me.

I'm seeing that most centri suited cams lift at .590 max so seems the extra lift is often not used. Also 114-116 is common lsa

There is a lot of mixed talk on duration.

[R8VXF]

Behold81 said:

ARAF said:

You need to plot lift over time, to get a graphic representation of the ability to flow. I'm sure Behold81 knows that though, as he's always been very hands on with his car.

Valid point. You want to maximise the flow you have. So holding it in max flow longer will be a valid factor.

I'm still learning on cam specs and whilst I get what a cam does and how differences will change the characteristics I'm still working out the finer points.

I read you still want some overlap to be efficient on performance. If I have read it right the cam stevie has is little to no overlap.

Iirc, with a charger, little to no overlap is better. Will see if I can dig the info out.

[ARAF]

Behold81 said:

I read you still want some overlap to be efficient on performance. If I have read it right the cam stevie has is little to no overlap.

Yes, but my understanding from the various arguments on here is that overlap will mean you exhaust a little mixture, and then you run into emissions problems. If you're okay with that, then fill your boots.

[R8VXF]

A very good read on cams in a blower situation: http://www.hotrod.com/how-to/engine/1409-lsx-blowe...

No overlap like on the BTR comp blower cam comes out top dog

[ARAF]

Ringram on Facebook said:

Someone should ask Behold81 why IVC and EVO are the 2 most important valve events. Then ask how that relates to the cam's in the linked article on the PH FI thread.. But that question will probably get banned because it might hurt someone's brain cell.

[R8VXF]

ARAF said:

Ringram on Facebook said:

Someone should ask Behold81 why IVC and EVO are the 2 most important valve events. Then ask how that relates to the cam's in the linked article on the PH FI thread.. But that question will probably get banned because it might hurt someone's brain cell.

I would say that this was because in the NA situation you need overlap to help draw the air in whereas, due to the nature of FI, keeping the exhaust valve open just wastes boost and fuel needlessly. Haven't quite worked out why the boost pressure drops just yet, still working on that one.

[Behold81]

ARAF said:

Yes, but my understanding from the various arguments on here is that overlap will mean you exhaust a little mixture, and then you run into emissions problems. If you're okay with that, then fill your boots.

Fair point. Emissions is less of an issue for me as I am not required to have a cat test.

Will read the article posted. I'm not saying I'm right at all. This is a bit of a school day for me in black arts.

[Behold81]

R8VXF said:

A very good read on cams in a blower situation: http://www.hotrod.com/how-to/engine/1409-lsx-blowe...

No overlap like on the BTR comp blower cam comes out top dog

Interesting read and it makes sense that boost is seen lower on an NA cam but it actually performed better than expected with the lower figures similar or better. On a centri that might be quite useful as it's not till 3.5k it really starts to pick up real vigor.

I can see some weeks of reading ahead of me!

Thanks all so far.

[MyM8V8]

MadMaxHSV said:

MyM8V8 said:

Bad luck Piers. Didn't realise you had them. ere they fitted at the time of the rebuild?

Yep went on during the build. This failure was a few years back.

Did you get a new set under warranty???

[MyM8V8]

Behold81 said:

ARAF said:

Yes, but my understanding from the various arguments on here is that overlap will mean you exhaust a little mixture, and then you run into emissions problems. If you're okay with that, then fill your boots.

Fair point. Emissions is less of an issue for me as I am not required to have a cat test.

Will read the article posted. I'm not saying I'm right at all. This is a bit of a school day for me in black arts.

The problem with the article posted is that is revolves around an extreme PD blower and as we know there is a massive difference between off idle performance given the huge torque produced low down in a PD blower. If you had that BTR cam in there with your centri you would probably be waiting ages for anything to happen and then at mid range the cam comes in together with the boost!

I remember years ago at TR seeing Stevie's(centri) setup break traction at around 150 mph (brown trouser moment for him I'm sure) as it all came in late on.

Having driven both centris and PD set ups, with your project, I would be looking for a cam that comes in a lot earlier pulling from low down and then let the centri do its job with boost higher up.

I think you want to be looking at a smallish cam to give you a good overall average increase in HP? With a road car, and given your mildish set up, why spoil drivability, you don't need to, and you certainly wont need to choose a cam with overlap with its attendant problems? (That BTR cam has negative overlap and for good reason)

At the end of the day its ok for someone to come on here quoting a project elsewhere but..... from the article "BTR's blower cam was obviously the hot ticket for this supercharged LSX,"

Would it be right for your (completely different) package? If you like the idea of a BTR cam, why not call him for a recommendation. Pat Guerra is also a good port of call for about 25 bucks.

All IMHO of course.

Edited by MyM8V8 on Saturday 28th February 08:53

[stevieturbo]

MyM8V8 said:

I remember years ago at TR seeing Stevie's(centri) setup break traction at around 150 mph (brown trouser moment for him I'm sure) as it all came in late on.

The brown trouser moment was at 190mph when it broke traction at that event. 150mph was/is normal.

That has little to do with the cam compared to overall package, and when I actually tried to put the foot down.
Almost anywhere but a prepped track with good tyres, it's only when into 5th there is usually some traction unless I tread carefully with the throttle

Although TR was with a slightly bigger EPP/Brutespeed cam they seem to use in everything 232/240 on 115, and also a larger 6.6/403
It didnt idle as nice nor rev just as hard as the smaller cam. It maybe had a little more mid range.

After that I downsized from a 6.6 to 6.2 and changed to the GT9 cam. This was definitely a less aggressive setup, and overall I would say no decrease in performance at all, and back to a totally smooth idle which I really wanted again.

But still not enough rpm's for me hence the change again to a slightly softer cam albeit in a solid roller this time hoping to see peak power around 7k

[MadMaxHSV]

MyM8V8 said:

Did you get a new set under warranty???

Dropped them a mail but didn't get any response.
Needed the car running so had a new set on order anyway and haven't chased it any further.
See the old set as spare parts should the same happen again. Spare rocker pair in the toolkit now.
Have to thank Stevie again for getting me running with a spare set and pushrods at short notice for the speed trials.