Originally Posted by racer7088

Friendly Freddie,

I would back way off of the compression and run a lot wider LSA right off the bat if you are going for more power with the nitrous. Tightening your LSA BUILDS compression and certainly does NOT bleed any away! Anyone telling you that you need to tighten LSA as you add compression is just plain wrong or doesn't understand camshafts very well. Tightening LSA is for classes where you can't make good compression and/or where you have tons of exhaust flow and low backpressure compared to your intake capability.

Tightening LSA opens the exhaust later which hurts power on NOS and it also closes the intake earlier which increases cylinder pressure down lower in the rpm band but may even reduce power overall depending on the engine. With the compression you have I can't imagine needing too tighten LSA or advance the cam much at all! Tightening LSA also increases overlap which is also NOT where you want to go on a nitrous engine unless you have huge exhaust and even then 110 is too tight. It is just increasing reversion.

I would have a cam probably much wider in LSA with a fairly large split to the exhaust side in duration. You need to size your exhaust lobe such that it can handle along with your headers and exhaust system the power you are aiming to make on NOS. The cam you have is not one that is going to make big power on NOS probably. Your intake lobe is big enough but certainly not huge and you shouldn't really make power as high as you are turning it anyway.

Also If you could leave on a little less NOS and phase in the extra NOS at even higher rpm your gaskets will live longer. Most people spray too much too soon and the cylinder heads simply lift and /or detonate. The LS1 just isn't the greatest on the head gasket situation that's for sure! Spraying 300 at 2500 rpm is 600 ft pounds more tq and spraying 300 at 5000 rpm is 300 foot pounds more tq and spraying 300 at 7500 rpm is only 200 foot pounds more tq.

Originally Posted by Friendly Freddie

Erik , I will keep all of this in mind. Thanks for all of the usefull info. I hope we all learn somthing from this little experience of mine.

BTW, I have a progressive controler on the car. I leave on 10% of total power and ramp it to 100% over about 1.5 seconds. The car 60 fts 1.21's and 22's pretty consistantly on a good track. I have never had spark plug issues and A/F ratio is very conservative. I think fuel and N20 is divided pretty evenly because of the Carb style intake. I say this, because I don't think the tune is the issue here. I would'nt want to back it down any because the 60 ft is what makes the car a quick as it is (it has never run out the back door like it really should).

Originally Posted by racer7088

If you fix the cam you will see a lot more on the back half.

Originally Posted by GrannySShifting

That motor is probably having a problem blowing down the cylinder at rpm, and Id take 3 full points or so of compression out of it. Getting rid of cylinder pressure is your friend when lifting heads.

Originally Posted by Friendly Freddie

I REALLY wanted to drop this bomb in the "advs/disadv of rod length" thread , but I figured it might ruffle a few feathers by disrupting the present topic of conversation (although its changed about 4 or 5 times already ). Its hard to get really good information about this from true experts.

Moving on , I have a 358 inch LSX engine in my race car. It was originally assembled for use in the LS1tech series extreem mod class which was an all motor class. We kept it under 360 inches to get the wieght break. We soon found out that to get this little engine to 60ft , it needed so much converter that it was no longer efficient on the big end of the track. Faced with having to put a jerico(sp?) in the car or do something else with the engine, I gave up and put a plate system on the car and decided to have some fun. The camshaft was sourced from LSM , and ground specificly for NA use. Is there a possibility I will see a gains from a cam change if I get one targeted towards N20 use? If so, why? and what are the differences between an NA specific and a N20 specific cam.

I know N20 is a dirty word for "real engine builders". I also realize that this thread is kind of "self serving" , but there is not a whole lot of really good info out there on this topic. I think all of us N20 addicts would benifit greatly from a truely intellegent conversation on this subject.

Originally Posted by Ben R

What was the first clue?

Originally Posted by 1936FordPU

Friendly Freddie's setup sounds alot like KECHME's old car.

Originally Posted by 1936FordPU

Friendly Freddie's setup sounds alot like KECHME's old car.

Originally Posted by Patrick G

It seems to me, that if you lower cylinder pressure, you will also lower hp and tq. I don't believe this is the answer he was looking for. He may just need heads with thicker decks or a more robust gasket setup (like o-ringing).

Originally Posted by Patrick G

Here's my very academic opinion on your cam setup. Basically, it sounds like your cam is spec'd very well for naturally aspirated performance. When running a 300 shot, it's not going to be necessary to deviate from the intake valve closing point that you're using now. Basically, you can keep the same intake duration and ICL as before.

But because nitrous burns the charge so much faster, we need open the exhaust valve quite a bit earlier to cut pumping losses and retard the spark enough to keep our peak cylinder pressure occuring around 13-15 degrees ATDC.

Assuming 110 intake centerline, the current IVC is 62 degrees ABDC and current EVO is 64 degrees BBDC (at .050"). Common nitrous practice would recommend opening the exhaust valve about 10 degrees earlier for the 300 shot and backing timing about 8-9 degrees from what was optimal NA.

That said, a nitrous dedicated cam would look more like this:
264/276 113LSA +3
Same 62 degree IVC
New 74 degree EVO (now 10 degrees earlier)
2 degrees less overlap at .050"

Again, this is a very academic approach, but will get you in the 90% range of what is ideal. I'll leave getting you the last 10% to the experts and to track testing.

Originally Posted by Friendly Freddie

It's the same set up I've always had. 1936FordPU (aka V6bird), I thought you knew I was over here at Friendly.

Originally Posted by racer7088

I can't tell you the hundreds of situations where a cam company promised people I know to pick them up and did not. I'm not saying that the problem was just the cam but I've seen one too many "cam gurus" in my lifetime already and most don't know a damn thing and I am NOT talking about anyone in particular because I actually like most of the "cam gurus" I know but I think you know what I mean! The guys from LSM and Camking are experts in their field of camshaft design and manufacturer and are NOT what I am talking about in general as well so I am not talking about them.

LS1Tech is quite simply the most cam obsessed and cam driven web site on the planet! People on this site have routinely told me how they could tell the "difference" between cams that were actually the same! I just don't say anything anymore.

Originally Posted by Patrick G

It seems to me, that if you lower cylinder pressure, you will also lower hp and tq. I don't believe this is the answer he was looking for. He may just need heads with thicker decks or a more robust gasket setup (like o-ringing).

Originally Posted by Friendly Freddie

I am of the same opinion that lowering compression (by a large margin) will slow the car down.

Originally Posted by EDC

Originally Posted by racer7088

Yes it is but I am encouraged that people are at least talking about all this stuff. The problem is that there are still guys telling people like Friendly Freddie that you can increase overlap and "bleed off compression!" This is the stuff that scares me and I hear stuff like that everday. People should know better. Even with all the cam talk on these boards though I just never stop hearing the crap like that.

Originally Posted by Friendly Freddie

Erik, Bryan from LME just informed me that my compression is more like 14:1. I think I'll do something to back compression off just a touch.

I for one, really appreciate you guys that are "in the know" chiming in to help the rest of us out. I like to think I'm a pretty intelligent guy , but I don't know about a lot of the more complex things that are going on inside of a combustion chamber. I want to talk to people that are more versed in these areas and be able to make an informed decision. They say "jack of all trades, master of none" , I don't want to fall into that category.