Hey all, looking for some insight again.

So I have got my car running great with new turbo set up. AFRs are now consistently very close to 11.8 (occasionally goes richer, I am okay with that) under boost, and close to the recommended values I could find for below boost (~14.5 cruising, 15 for idling and very light load, dropping down to 12s until boost, where it drops to 11.8). Everything is going according to my research and expectations, and I am taking it slow conservatively street tuning my car.

Currently I am running only wastegate pressure at 5lbs until I have thoroughly tested and adjusted my build. I am going to shoot for a final boost pressure of 10lbs.

Right now my issue is this:

I am getting 1-2 psi of boost creep at redline (7lbs is highest I have ever seen). My thoughts are this boost creep is an artifact of me running extremely low boost for the size turbo I am running (.57 trim t3/t4). (I am way under the efficency range right now, and will just barely be in it at 10psi, I know this is not ideal, I am researching different turbos currently)

My theory on why I am getting a small amount of creep is because I am trying to run such a low boost level with this turbo, and that it should likely go away when I increase my boost. This is supported by my research, that being said I am not going to do so until I am sure.

Taken from wikipedia (one of the places I researched, by no means the only):
"big turbo/low boost = bigger wastegate
big turbo/high boost = smaller wastegate
small turbo/low boost = bigger wastegate
small turbo/high boost = smaller wastegate"

I am using a 38mm external wastegate, my ram-horn style manifold has the wastegate mount in a similar location to most other ones I have seen, and the opening for it was smoothed and port matched rather well. This is another reason I do not think it's an issue with my wastegate setup.

The final piece of evidence that leads me to this conclusion is that the boost only ever creeps to 7lbs, which leads me to think that this is the max boost it would creep to regardless of my wastegate settings, which is less than my target of 10lbs.

Anyways, any insight you have would be great.

Thanks everyone,
Matt

 

all depends on the placement of the wastegate, but ramhorn's with 38mm wastegates are known for creeping, and 2lbs isn't bad at all. Also, just because you have a 5lb spring, doesn't mean its going to be 5lbs. its usually an around about figure. Not everyones setup is the same so the spring cant possibly be 5lbs on everyones setup. Just be glad all yours is creeping to is 7lbs, some people have way worse creep issues.

 

The wastegate placement on the manifold plays a big factor in how efficient it can bypass exhaust.
But essentially you are correct, at low boost you need to bypass more exhaust than your WG is capable of, hence the boost creep.

 

The spring seems pretty accurate in my case, it climbs to 5, then holds stead until the high end of RPM range.

My main question is, if I get 2lbs of creep from a 5lb lb setting, does that mean I will get even more creep at 10lbs? Or will it be steady, since it seems the maximum creep and 7lbs and I would be using a boost controller to keep the wastegate shut until well over 7lbs?

I just don't wanna accidentally creep up to something like 12 or 13 psi. I am gonna set my ecu to cut out at 11psi to be safe at any rate.

 

Lemme guess. Using Hondata as your boost control? That amount of boost is not way out of the efficiency range of a 57 trim using a 38mm gate. We've done that for over 12-13 years, even on a Kooks. No creep.

 

the more boost you run, the less it will creep.

it can be creeping from 1 of 2 things, or both:
1) size of the wastegate. higher rpm flows high cfm, and small wg's can become restrictive if they aren't bypassing enough exhaust even when fully open.
2) ANGLE of the wg pipe where it connects to the manifold. the actual placement of it really doesn't matter, it's the ANGLE that matters. ideally it should be at a perfect 90 degree angle where it mates to the manifold. angled away from the turbo will cause boost creep, angled towards the turbo will actually cause boost drop. higher rpm causes higher velocity exhaust. higher velocity causes it to blow past an angled wg instead of blowing out the wg, increasing air volume/velocity across the turbine wheel, thus creeping boost

 

I am using a neptune RTP for engine management, no hondata. But to answer your question, no I am using no boost control currently. Just a 5lb wastegate spring. I want to thoroughly test my setup before adding any more boost than necessary. 5lb spring was the lowest boost I could have. In the future I plan on upgrading to a electronic boost control system, mainly so I can have lower boost in first and second gear.

Currently I am planning on installing a manual boost controller (ball and spring) with my 5lb spring, solely for increased spool time. If I didn't care about spool time I would just use the 10lb spring I have sitting at home.

My wastegate is mounted perpendicular to the collector, right before the turbo inlet. The wastegate inlet was smoothed and rounded when I got it.

Based on everyone's responses and my research I think it's safe to assume the creep is due to my low boost setting. I will install a boost controller and start slowly working the boost up to my target.

On the note of turbo efficiency: when I looked at the compressor map for my turbo, and used a online calculator to generate the flow map for my engine (d16z6) using a VE of 85% it showed that at 10lbs I would just barely touch the bottom edge of the peak efficiency range of my turbo when close to redline. At 5psi I wouldn't come close. Could it be I used to low of a VE in my calculations? At any rate, this is good news.

 

creep is never normal, it shows that some part of the system was designed poorly/improperly... most of the time it all comes down to turbo size, boost pressure being run, wastegate size and placement on the manifold, as well as the style of manifold

 

Yeah, for sure. But from what I can tell it is being caused by me trying to run to low of a boost level for the setup I have. But, since I am only running 5lbs to test my install for a few days before going to 10lbs. I don't think it is a huge issue. Experimentation will tell for sure though.

 

it's definitely not a huge issue. 2psi of creep is very small all things considered. more than likely, when you raise it to 10 it will hold 10 rock solid across the board.

I did an install of an ebay kit once, 6psi spring, hit 6psi at 4k, held it steady to 5k, then crept all the way to 14psi by redline

 

Yeah, that's what I was thinking. But confirming it is good, I figure since I cut a corner using a cheap kit, I can't afford to cut any other corners!

On the up shot, been running it for several days now. I have over a hundred miles on it, and so far no major issues. The oil feed flange was weeping some oil at first, but I tightened it up and it's fine now. Still going to replace with a better flange and line for my own sanity. The quality of the exhaust manifold and downpipe are surprisingly good, rather thick walled tubing, and a decent grade of stainless steel, as there is no signs of rust showing, despite having been run for several days in the rain (no hood). All the inner welds where ground down and matched to the gaskets.

We'll see how long it holds out, going to check over the entire system in a few days and see how everything is doing, and pull the turbo and exhaust around 1000 miles to check it over (and also fully wrap the exhaust). Judging by the response of the turbo though, everything seems rock solid. Maybe there is something to the rumors of improving quality in ebay kits. Maybe I lucked out. Only time will tell.

Just gonna keep the tune very conservative and watch my sensors like a hawk. Worst case I will change to a rebuilt 14b over the winter. Won't be driving the car anyways.

Thanks again for the input, I really could not move forward without everyone's continued insight.

-Matt

 

Personally I like a little boost creep on the low end. It will mean boost wont taper as hard on the top end when you start to push it harder.

 

Yeah, that makes a lot of sense.

Now I just need to double, and triple check my equations for maximum possible power output from my setup at a given PSI. I want to make sure I am not going to go beyond 200-220hp under perfect conditions. That way I have a big safety margin with my engine. (Everything I have read says 220-250 is about the maximum reliable output of a stock D16Z6). Previously I calculated ~218 hp at 10psi with the turbo I have, so I imagine in the real world it would be quite a bit less, especially with my conservative tuning strategy (rich under boost, with timing retarded 1 degree from stock per lb of boost...essentially leaving it alone on my basemap). Should be a pretty safe goal, I think?

So far all my research and calculations have been a pretty good representation of results...Lets hope it stays that way, eh?

 

yea creep on the low end is fine, but it has limits.

I feel his setup is creeping as the result of a large-ish turbo, small wastegate, and the low boost being run.

When he gets his setup to 10psi, it (hopefully) shouldn't creep. but if it does either run more boost, put a softer spring in the wg and use an mbc or ebc and the softer spring will mean more valve travel for a given psi and normally eliminates creep issues on normal setups

 

I am planning on running a 5lb spring with a MBC, eventually switching to a EBC controlled by my NepTune RTP. I planned on doing this to improve spool times, but if it helps avoid creep that is a great added bonus!

 

Yea MBC's do their jobs well but if there's an issue with the setup elsewhere that causes creep then there isn't much it can do about it. Having something like a MAC solenoid and your ecu controlling boost then you can cater the boost pressure properties to your liking.... things like how fast the car builds boost, boost by gear, boost cut, etc

 

Yeah, absolutely. That's why I want to upgrade. I just happen to have a decent MBC sitting on my desk, while I need to order parts to do the ECB.

 

the d16y8 I mentioned above that creeped to 14psi made 327whp on a completely bone stock motor. it held up perfectly fine for 10 or so dyno pulls at that power, and 5 or 6 pulls in 2nd and 3rd gear and a short burst of 4th gear on the street. I ended up lowering the rev limit though to keep boost below 10psi because it still had the stock map sensor and couldn't read over 10psi. still made 250ish, and last I knew the owner had over 80k miles on it since with no changes, besides the ebay turbo seals wearing out and needing a rebuild.

just sayin.
not saying it to tell you your engine can take 327 reliably lol, just sharing :p

 

Yeah, that matches my own research pretty well. So I am fairly confident my engine can take 10 psi with a conservative tune, assuming my figures were right and 10psi in my configuration yields a upper number of about 218. (really think I will be well below that.)

Getting 250hp at 10 psi is a bit concerning to me. It makes me think I did my calculations wrong, as I got a 'perfect world' number of ~218 @10psi, with a fairly large turbo. 30 horsepower more from a similar engine makes me think I figured something wrong on my end.

My calculations: https://honda-tech.com/forums/showth...0082&styleid=2

Obviously I don't expect my numbers to be exact, or even close for real world...More of just wanted to have a upper POSSIBLE limit well below 250 hp. (Real world I would like 200-220, traction already sucks a bit at 5psi, which as far as I can tell gives me a upper limit of like 160-170hp, probably less...need better tires. lol).

 

The Manual Boost controller is fine, especially if using a lower than 10psi spring. (This is what we did way back when FMUs and AFC Hacks were still the standard on the stock map sensor with a Synapse "Missing link", (similar to a one way aquatic check valve) where the MAP sensor was completely bypassed for the 10psi limit.

The T3/T04E 50 and 57 trims at 10psi for either engine platform, either D or B series, can do the 250whp, its just a matter of making sure you're not concentrating on PSI so much, and look more to your management, supplemental parts and your tuner's ability to work with it.

 

Yeah, I am testing the boost controller (hallman mbc with ceramic ball and heavy spring, wanted light spring but came with heavy. free, so can't complain) right now it is set to 8lbs and works great. I hit positive pressure at 2500 and full boost between 3500 and 4000. Wastegate snaps open at 8 and holds rock steady at 8. No spiking, no creep. Accidentally went to ten prematurely for a pull, ran great. Down at 8 until more testing and tuning is done. AFRs look great and steady though.

I know they CAN do 250, my concern was my calculations with my turbos compressor map indicated I would only be around 200 at most with my setup at 10psi. So I want to know where I made an error in my figures.

 

it's very difficult to get an accurate number based off known numbers from lower boost pressures. the variation is typically the volumetric efficiency. and the VE for an engine is usually different at different boost pressures. IE: my engine ran about 85% VE at 3500, 100% at 4200, 124% at 4800, 94% at 5800 when at 6psi. at 9psi it changed to 93% @3500, 92% @4200, 118% @4800, 105% @5800. I don't remember the figures above 6k, but it changed weirdly up there too, some higher some lower.

the reason for this is:
1) pulse tuning in the intake manifold relies on the speed of sound. but the speed of sound increases as air density/pressure increases, so the effective rpms in the pulse tuning changes, altering the VE by number and rpm.
2) cams. airflow characteristics in/out of the cylinders change a decent amount when intake charge pressure changes.

 

I was mostly trying to get a maximum amount of HP possible for a given amount of air the turbo would flow at 10psi. Shouldn't that be mostly independent of VE of the engine?

I figured if the maximum amount of air the turbo could move would make 200, it would ensure that things like VE and such would keep it well below 200.

Matt

 

Nope. in fact VE would play more of a role, not less.

 

Is there a reason you're stuck on 10 psi? Why not just use whatever level you need to achieve your power goal? A map sensor is only a hundred bucks.