LS-Vtec boost questions

ASSISTANCE Forced Induction
1

Mod List -

B18a1 Block
B16 Vtec head with GSR cams
LS Vtec kit / sandwich plate
CTR pistons
LS rods
ARP rod bolts
GSR water pump
obd1 ecu

So i picked up this motor with just under 50k miles, its a really strong running motor and i dont have any problems with it other then i still havent had a chance to get it tuned. When i got the motor the guy who built it said i the only thing i couldnt do was boost this motor because it had to high of compression? would that just be his choice of the CTR pistons? ive searched through other ls vtec builds and obviously people boost them, ive been trying to find build threads of what all people were using but i feel like i have come across ones with the same CTR pistons in there builds.

Basically im wondering at where the motor is now, what would i do to prepare for boost? ive been looking into turbo kits but do i need to change out pistons and rods? is there anything else crucial that needs to be done? im not looking for alot of lbs, just something to give it some go power.

thanks for any responses, im still continuing to search for my answers with the help of google and this website, but straight answer from someone knowledgeable would be appreciated.

2

Use a site that has a compression calculator…

Www.ZealAutoWerks.com has a great b-series calculator with a ton of OEM options that make it easy to determine compression on a motor.

B16B pistons are really a AllMotor piston… the dome is EXTREMELY big.

According to that calculator, those pistons with a B16 head results in 13.7:1 compression.

That is VERY VERY high. And you say unturned? Very dangerous.

And not just that, piston-to-deck height is -.015". That means the top of the piston is only .015" from the deck of the motor. Very tight clearance… Which is fine, but it severely reduces the selections of cams you can run.

GSR cams are great for turbo…

LS rods are fine for boosting, as long as the fasteners are upgraded. The ARPs are perfect.

Either replace those pistons with a LS/B16/GSR/ITR set, or get new aftermarket pistons and new aftermarket rods. Match them… OEM rods with OEM pistons, or all aftermarket.

Tuning should be a very high priority. If you’re ‘building’ a motor, tune it. Don’t rely on a stock computer to run a motor that is NOT stock. Makes no sense.

Not only is the health and longevity of the motor on the line, the total power output will be greatly reduced without a quality tune.

My tuner made my basemap, and then tuned my setup… I gained 60wheel-hp on my mild LVtec setup after being properly tuned. I guarantee your current setup is suffering badly because it is untuned.

Feel free to browse my build thread… the specs are all in the first post, with dyno vid and chart on page 12.
http://forums.g2ic.com/showthread.php?203377-Long-build-in-process

Compression with boost is a double-edge situation… Too low of compression and your car will feel gutless when not in boost. Too high of compression, and you’ll suffer from ‘detonation’… Which can melt down your motor, not to mention it is a LOT harder to properly tune.

You really want somewhere like ~10:1. Remember that ANY camshaft will reduce your “static” compression numbers because of the overlap. Also the same is true for elevation reducing compression… But it is best to simply play it safe and keep it at a manageable number.

3

Ya havent had it tuned yet, it runs really good… maybe a little rich but ive never had problems with it, and no real power after 5800 RPMs, but its just a low and slow daily driver right now, i dont think ive been over 80 mph and almost never over 3500 rpms. because of the fact that the ecu it came with was never tuned.

I was actually thinking about getting a tune done but then felt like boosting it would be fun and then just get it tuned after i did that, rather then tune it and a few months later have to do it again.

Ok so thats really high 13.7:1 for boost applications i should look for 9.0:1? 9.5:1? ive come across those numbers before, would that be the standard for turbo compression?

Anything else ? if i were to get different rods and pistons… is there anything else thats a must on ls-vT set ups?

4

Well, it depends on how much security you want… and how much money you want to throw at it lol.

My motor was very mild, and I didn’t want to rev the nuts off it because of it being an LS… Stock redline is 6,750rpm. With my R cams power drops off at 8k. That’s virtually 1500rpm higher than stock. I probably would have been ok without upgrading everything, but I went with ARP main bolts, ARP head studs and aftermarket rods with high-strength ARP2000 rod bolts… I wanted as much security as I could get. I’d rather my motor last, than blow after 10k miles because I didn’t spend $200 on head studs.

And that’s one thing to keep in mind as well… with boost you won’t have to rev to the moon, and those GSR cams will only make power until the factory GSR redline…

I completely overbuilt mine, but that was my sense of security. If i strapped a turbo to it right now (with proper tuning of course), I wouldn’t feel hesitant at all. It’s easily a 450whp motor.

5

I really appreciate your feedback man thank you, im going to go through your thread and start doing some serious research since funds are becoming available, thanks for taking the time to reply i love this forum.

6

No problem man… that’s what the site is for!

You’ll probably want to ditch the factory PCV system and use a catch-can setup instead. Freeing up those gasses will let your motor breathe a lot easier. At least look into it… boosted cars benefit from that.

7

here’s my thought… others may not agree with me but this is from personal experiance.

lsv with ctr piston would be 100% fine for turbo… the condition here is fuel type & size of turbo.

If your limited to 92-93octane I would stay with a larger turbo which creates full boost 300-500rpms after vtec.
This will make tuning easier & also greatly reduce any chance of detonation (granted tuner knows what they are doing).
Once high cam (vtec) comes up your static compression is really not high at all & 93octant is fine for 300-350whp (again with larger frame turbo).

If your on e85, you will have more turbo options avaible.
You can pick a medium size turbo like 55-57trim turbo.

welcome to the darkside

8

13+:1 compression is really not suitable for turbo…

With the small amount of power you get from one extra point of compression, you’re better off going lower and having something more tunable.

9

I’m not saying it’s ideal. I’m saying it can be done with proper factors as i have listed.

OP find out who your tuner is, ask what they feel “comfortable” tuning… each tuner has their own skills & experiance.
Just because I say +13cr turbo is doable & someone else says 10.1 is tuneable, your tuner may not feel comfortable with anything higher than 9.1 lmao. When i doubt go with your tuner. If you don’t like what he has to say, try another tuner.

to each his own

10

I read your provisions… I’m just not in agreement.

Having a set of pistons in your block that leave you with -.015" P2D clearance isn’t really the best idea either as it severly takes away your camshaft options.

Most of the SFWD guys that are hitting 900+whp are sticking around 11-12’ish:1

11

i’m not here to aruge with you, so please be mindful of that & lets not play the interweb ego measuring game.

This isn’t about who’s tuner is the best or what 900whp cars run for cr, so please let’s not go there.
Is your tuner OP tuner?
Is OP building a 900whp car?
If not why even mention it unless to try slam my argument?

Do you see how i tried to center my post back to the focus of the OP questions/build?
I hope you see that, maybe you’ll not try to attack me.

If you want to help move the converstation forward, please join me.
Moving on…

OP:

-.015 out the hole is not a big issue considering:

  • piston to deck clearance (in this case) has NO affect limits of aftermarket cam choice ***** see note below ***
  • you have a b16 head which has small amount of counter bore in the champer
  • your head isnt decked some crazy amount
  • your using oem headgasket and no thicker
  • your pistons are alum which do not expand same rate as froged piston.
  • whoever built your engine, hopefully made sure p2w clearnce was under .0020 to reduce piston rocking at higher rpms.
  • If p2h clearance was an issue you would have already known by now with a thread “why did my engine blow”

I have my own reasons why i think ctr pistons would not limit your aftermarket cam profile choice. Despite the piston sticks out (hypothectically since nobody has measured it) the block by -.015. If someone has a reason otherwise i’ll certainly listen.

Lastly OP, i’m assuming your not trying to make 900whp with your motor.
My guess is that you want 200-240tq and say 300whp.
please lay out your goals clearly.

Charlie

12

If you feel slammed by what I say, that isn’t my intention… We have remained civil so far, have we not? I simply disagree with your reasoning.

I’ve read quite a bit on why B16B pistons aren’t the best, and I’m of the understanding that due to the shape of them they create hot-spots in the cylinder which can’t really be changed by tuning.

But at the end of the day, yes, the tuner is going to be the “make it or break it” factor of prettymuch any build. As Charlie pointed out, speak with the people in your area and see what they feel comfortable dealing with. And your ultimate power goals will help in determining what is overkill and what is necessary.