Car setup:
b series 84x89
mildly ported head with .5mm o/s intake and exhaust valves
custom web cams
brad penn 10w-40 oil
Blox 76mm throttle body
3" aluminum piping
4" open downpipe
s372r 1.25a/r
12x24x3.5 intercooler core
divided front mount manifold
hondata boost solenoid set at 34hz


On the dyno last week we had a few problems. First issue was boost not holding to redline, I had 11lb springs in the gates and the car just wouldn't hold boost to redline (I think). The car would hit about 48lbs of boost at 8k rpm and then power would just drop off like a rock. We were also having some issues with hondata's datalog cutting out near the end of the runs so I'm not sure what boost was falling off to, or if it even was for that matter, but power was dropping off to about 650ish I think by 10k. This isn't really a problem I am going to try a few things like some bigger wastegate springs and maybe a homemade c02 setup, and I think I have the datalog issue fixed. Did a couple pulls at 835ishwhp level trying to figure things out and stripped 4th gear. Decided to up the boost solenoid to 100% and try 5th gear, we ended up making 840whp/590 tq on 48lbs. Once again peak power and tq was at 8k rpm and then it just tanked off to like 600whp at around 9500 rpm. On that run we lost the datalog at 8400 rpm and it was already down to like 42lbs. My conclusion is that I just have waaay too much backpressure for the 11lb springs. Didn't bother making anymore pulls since I didn't have any other springs with me.


Fast forward to today where it was pointed out to me that my compressor wheel is hitting the housing. The car has been running and driving for about a month prior to the race gas tune so when we were strapping it on the dyno I made sure to check the turbo and it did not look like this I am 100% sure.

There are scrape marks in the compressor housing. They are on the top and bottom and each mark is about 90* of travel. What has me puzzled is that its not 360* it is only at the 6 o'clock position and the 12 o'clock position.
I know my feed and return are fine. -4in/-10out. There seems to be substantial shaft play, but it doesn't hit the housing when I spin it by hand.

Anyone have any thoughts about my experiences? Anyone else have issues with radial clearances under high boost on the s372r? Does anyone else have problems holding high boost to redline with 11lb springs?

 

Also anyone know where I might be able to get a rebuild kit? Also thinking about putting a 87mm turbine wheel on so I don't have as much backpressure problems. Or I could just buy a billet 72....if I hit the lottery....**** maybe I'll just downgrade to the 67mm class.

 

What spark plugs are you using? I have had issues with datalogging at high rpms on s300 with non resistor plugs.

 

i have that same exact turbo with 11psi springs and it holds 13 psi of boost all the way to 10.5k rpm. have you checked the diaphragms in the wastegates?

 

damn

 

how do you have the boost controller setup?

 

Wear marks at 12 and 6 positions is signs of bearing wear, the shaft will play up and down but not side to side. Also extreme clamping force from an external clamp that holds your piping together may play in this too.

 

Yes we are going to try the iridium plugs. I have seen a few other cars that were fine without the resistor plugs, so I didn't think it would be an issue and went unprepared. Duly noted I won't make that mistake again.

I would need to check the logs, but I don't think I was having any issues at low boost, only 30+psi.

As far as plumbing wise...it's been awhile, but I think it's like this

You think I overtightened my vband clamp that holds the compressor cover on? Also I do have play in all directions except in/out.

 

them number seem low ive seen a billet 62mm make a little over 800 on 12lbs less and im sure my 6765 would make those numbers on around 35lbs. Is there some kind of restriction in your setup you are over looking? You might be better off with a billet 67mm you will LOVE the power band!

 

I made those numbers at 8k rpm...I think if it would have held boost it would have made significantly higher numbers.

 

oh ok my bad i see didnt realize it was droping off that bad. But yeah if you went with the billet 67mm you would be more then satisfied i know 2 people this year that ditched there 372's for billet 67's and they love em!

 

I think a little more info on the cams might be needed as well. MY s372 made about 840@34psi, im wondering why you are having to run over 40 to achieve those kinds of numbers?

Also an 11psi spring is just way to low for that kind of setup, i had to run about 18psi worth of springs to get mine to consistently hold boost at those levels. I have seen people well more than double a spring with our types of setups but your fighting the way it works doing it, eventually it will give you issues.

I was running a set of pro1s in my car and my car would start to drop off after about 9400 with my particular setup, but i was very happy with what it did.


as far as the datalogging goes, that has always been an issue, it can be the plugs, vibrations, engine noise, ignition feedback from MSDs or other boxes, etc. best thing hands down is to setup the internal datalogging and use the grounding switch, it never fails

 

One guy making over 800+ on a billet 62 does not constitute that everyone owning those will be able to make that power. Now stating that someone with a billet 67 or cast 72 can make an easy 800 is a more sensible way to put it.

Your problem with the compressor wheel scraping is a good explanation for why you are having boost drop off...once it gets to that point its like hitting the brakes...especially if its making deep scuffs. The rebuild kits for these turbos run about 150$ plus shipping from Bullseye, and if you want bullseye to do it its 250$ plus shipping and that includes everything. Just an FYI. I would figure out why your turbo did this and move on with the same unit...did you break in an engine with the turbo connected? I've done that several times and never had any issues but Bullseye states not to do that.

Mr Sponge, I also make 850 at about 34 psi on my 372, i run a 13psi spring x2 and it maxes at 35psi on the dyno but can go to 40 easy at the track.

 

Yes I did break it in on the dyno. Good to know that it's not terribly expensive for the rebuild...Plan right now is to just rebuild the tranny, put some bigger springs in and take it to the track. Hope it all holds long enough to get my license. Setbacks like this really hurt.


has anyone ran 48+lbs on a s372?

 

that thing is gonna go beyond 250$ in repairs if you go pushin on it like that trying to get license, etc.

 

You will see a lot of boost like that at low rpm, but you won't get it to hold 48psi to redline, not on the dyno at least. On a good day i'd get mine to hold about 45psi to redline in 4th, wouldn't even come close in 3rd.

You have something else going on, but even when it's corrected, the compressor will run out of air and boost will fall with rpm when it's run at it's limit.

 

Yeah I know it won't hold 48 all the way out....but based on the power at 9500 it can't be making more than 30lbs....I would think 11lb springs would make more than that...maybe not maybe I have even other problems....regardless it's all just speculation and completely pointless without datalogs. I'm so frustrated. I appreciate everyone's thoughts and insight though!

 

if it is falling off at high end it still should be flowing close to it's rating even when boost is falling off, so it should still be flowing 95lbs/min which I can't see how that = 840whp at 8k rpm and 650whp at 9800rpm.

 

I agree, there is definitely something else wrong, just mentioning the boost thing as there is a lot of confusion on that kind of stuff.

 

Narf, you really shouldn't be using the numbers that we saw on that single 5th gear pull for anything.

It only hit 48psi @ 7100rpm because of the load it saw in 5th gear, it won't do that at the track. Also, boost had dropped off by 3-4psi by 8300rpm and it went super rich, which caused the power to fall off horribly. It sucks that we kept losing the datalog at higher rpms, but we know it was dropping boost at high rpm. It's to be expected with those small WG springs.

Add in the fact that we don't know when the compressor wheel started contacting the housing, haven't made any cam timing adjustments yet (since we've not used those cams before and don't know where they will want to be at), and we lost 4th gear before being able to finalize the AFR and timing at higher rpms/boost. All those things need to be taken care of and further tuning performed before I'd get overly concerned about it not making the expected power levels.

 

Agreed. That was a high compression setup as well which greatly affects the power per psi. This car is pretty low compression, only 9.0:1 c/r.

This too. The cams seemed very mild, car had 19"/vac at idle. I didn't even think to setup the internal logging when we started losing logs, should've tried that. This is actually the first car that I've had issues with losing the datalog in S300 while on the dyno, even with non-resistor plugs.

 

Even when we were in 4th gear at lower boost levels it was doing the same thing 835whp 533 tq at 44psi...I definitely don't think my car pulls 19" of vacuum LOL.

I'm just really frustrated....it doesn't help much that I've had 2 days off with nothing to do and this is all I have to sit and dwell on.

Something else I've though about... I'm kinda wondering if maybe my manifold is cracked or something which could be why my car is louder than everyone else's 4" open downpipe cars and it's just losing exhaust energy up top.

 

If I may ask what did you set the Lobe centers at? And for the comment on it being a mild cam, I don't agree with ya. That cam is 260 @ .050 so it doesn't have no problem takin the power above 8k rpm unless the lobe centers are way out of wack

 

110/110 but it was my first time degreeing cams...I might have messed it up...the cam gear settings ended up being +0.5 on the intake and +1 on the exhaust. I don't think the cams are the issue.

The main reason for my post wasn't a "why are my numbers low" or "why am I not holding boost" I was just giving background info really and if anyone had any thoughts on those things sure they can chime in. My real question was if anyone else had hurt a s372 because of 45+lbs of boost. I know the 48lbs I saw was unrealistic for a real world boost number, but my point was that it did make 48lbs of boost and I was wondering if that might have hurt the turbo causing some radial clearance issues. It seems the obvious concensus is no now, but I wanted to ask.

 

I don't know enough about the cams to speak with any real authority, I just noticed that it was pulling 18-19"/vac at idle, thus my comment about them seeming to be pretty mild based on that.

I'm pretty sure they are less agressive than the Pro1's usually used on a build like this because that's the whole reason he switched to these cams - there wasn't enough V2V clearance with the OS valves and the Pro1 cams. And the power wasn't dropping off until 9k+ rpm, not 8K.