China 2871 dyno run built 1.8l 280hp 250tq 20psi
 

Here is my recent dyno tune. It's a load Eddy steady state dynojet 224XLC. I was going for a safe tune that would give me no risk for detonation. I was hoping to break the 300whp mark at 20psi, but it didn't happen.

There was a strange intermittent drop at 6k rpm that we think is coming from my cop harness. I've bought some replacement cop connectors with wires already attached to eliminate my shoddy craftsmanship.

Two runs are logged. The "clean" run and one with the drop.

Where do I go from here? I'm going to get a Map Daddy sensor so I will feel comfortable going to 24-25psi. I think the standard diypnp sensor is only good for 21-22 psi. Someone correct me if I'm wrong. Before increasing the boost to that level, I am going to dial in the closed loop boost settings. The steady state tuning of the none boost cells made for a very nice drive home.

My diypnp psi and the dynojet differed by about 1 psi. The diypnp was about a pound higher. He pulled his point from a vac port on the front of the manifold. I pull my MS reading from a port that is shared with the fuel injector rail. Should I change mine to a different spot?

Feel free to add ideas, areas for improvements, thoughts on what could cause the intermittent drop at 6000rpm.

Also this is with an intake cam gear retarded by 7 degrees.

Fourth gear pulls with 6sp and 4.10 rear



https://www.miataturbo.net/picture.p...pictureid=1346

https://www.miataturbo.net/picture.p...pictureid=1345

GREAT power, and wow, almost 300 lbs of torque at the wheels, congrats!

As much as I'd like to stroke your ego, 280whp at 20psi is a little lackluster, especially with an ARtech setup and retarded intake cam. Your timing map isn't particularly conservative either (16 degrees at 240kpa) - I'm only 2-3 degrees up on you (~19 degrees at ~220kpa). Before the Honda IM and E85, I was seeing ~265whp at 14psi, and on the old '99 motor it was 300+whp/wtq at 18psi.

Two theories: Either there's some .64 A/R housing phale occurring, or the chinabay 2870s aren't performing like a genuine Garrett does. Phil had the same thing - 2870, 26psi and water injection producing less than 300whp/300wtq.

The setup looks good - good manifold, good exhaust, I like the retarded intake cam gear and all the rest of it, but something is lacking for sure.

This has been said already by many actually.
Specs aren't the same, so output is not the same.

Still not bad IMO.

I was thinking the exact same thing. I was a bit surprised that the 300HP mark wasn't surpassed.

I think it is what it is. The china turbo seems to spec close to the 2871, but maybe there is more to it than impellar/housing size. At least we are getting some data on these turbos. On a positive, the turbo only costs $300.

Maybe after a hardtop and 3.6 R&P I will venture into.

My IC piping is only 2", I don't know if that would be an issue. IAT was just shy of 100 degrees.

BB turbo's always make more power. Even with the same specs. From what i've been told. Even a Garrett 2860 potato will make more than that at 20psi. But for the $1000 saved, I would say your doing pretty well.

The cost to power benefit is why I'm not seriously pissed. It's hard to complain about saving a $1k, Plus my built motor can handle all the boost this can throw at it. I'll just take it to 24-25psi

Car must be a handful to drive now. I just got a chinabob2871, hope i can look forward to close to the same numbers

I hit 298/296 on a mustand dyno with my inferior 1.6. I would add some water injection to your setup and go back.
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We were hitting 260rwhp (dynojet) on newbsauce's .020" over 1.6L with a true 2871; only 17psi.

I don't know what to tell you guys. My options appear to be: raise boost or new turbo. I'm not going to buy a new turbo.

Water injection.... retune (and add boost if necessary)

all of the above.

I'm not going to hassle with water injection. How does my tune look? Rides really smooth through all of the cells up to 20 psi. I'm currently trying to pull out the extra enrichments that were present when I was tuning. This is proving to be harder than i expected.

enrichments/trims are a very finicky part of the tune to mess with. be careful. save the map often (under new file) so that you can always have a "restore point" so to speak

I found that out on the way into work this morning. I made too many changes at once. As soonas it came out of warmup I had to pull over and use my good dyno tune. I'm going to start slower this time.

Warm up was constantly adding 13% after it reached temp, so I figured I could just shut it off and add 13% to my ve table.

Without seeing a log file of how the AFRs react to your VE table I can make the follow assumptions:

It goes hella rich as it's building boost and it leans up as the RPMs increase in boost.

go back and do it in the right gear. 4th gear if ur running a 5 speed. 5th gear since ur running a 6 speed.

doesn't matter on a dynojet. youre just pushing a concrete drum and it calculates the gear ratio.

Water injection is so easy buffon could do it.
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The dyno is 3 hrs from my house. I already paid $450. The cruise cells are good, the intake cam is good, and my timing is good. Are you suggesting I do a few pulls on the street datalogging and adjust myself, or go to a local dyno and pay for a few pulls on it.

The 9-25 datalog is from the last pull on the dyno, and the 9-28 log is from driving to work this morning.

If the tune can be improved, it's hard to blame the dyno guy for my lack of understanding of the settings in MS. I don't have another 450 to spend right now.

I don't mind if people think my tune is shit. That's fine, and feel free to voice it. Just leave some constructive criticism about the best way for me to rectify the situation.

You could tune it yourself. You have a good baseline. Adding wi should allow you at least a couple degrees worth of spark and maybe a bit leaner mixtures. Which will result in finally reaching that 300whp goal of yours (if that's your goal).

what sorta o2 sensor your running, cause your logs always show you're crazy rich in boost.


running 10.8:1 in boost =/= power.

AEM. We tuned off my wideband not his. He said the location of mine was superior to his in the tailpipe anyway.

I guess I need to do a few sustained road pulls and review my logs.

WI is too much hassle for me. I'm going to get what I can out of this turbo and be done. I will however add a Map Daddy unless people think I can push the standard MS mapsensor to 25psi

What is a safe AFR at 20-25 psi

More to it than just "safe for xxx psi". But mid 11's is never dangerous. Low 11's if you wanna be super duper safe.

I guess I'm trying to determine if AFR needs to drop linearly with boost, or does it look more like a decaying exponetial. i.e 3psi 12.8, 6psi 12.4, 12 psi 11.8, 15psi 11.5, 18psi 11.3, 20psi 11.3, 25 psi 11.3

don't go richer than 11.5. otherwise that looks good.

I let mine stay fairly lean below 4psi since I do retard timing at the same time. Since my turbo is smaller, I find myself in boost quite often.

http://www.boostedmiata.com/gallery2...gets_msIII.png

I have a similar afr table. I'm a little leaner at idle and richer in boost. You also have a nicer transition between just off idle and cruise.

Just to clarify before I blow my shit up. When I am boosting to 25psi, I don't need to go lower than 11.5 afr???

I acutally idle at 14.7-15.0:1, that's an old map.

yeah, it's just wasting fuel after that. there's no more oxygen to burn.

I think your confused about pressure and afr, when you are in positive pressure your afrs targets dont change from 10psi to 25psi.

Did I miss it, what gas are you running? All 93 octane is not created equal. What CR pistons? 8.5:1, 9:1?

Not sure why that drop couldn't be some detonation either. Was the clean run the first or 2nd run?

I'm aware that AFR at 12 psi and 25psi would require different amounts of fuel to reach the same AFR. I was concerned that the increase in pressure would increase the heat enough to increase the likelihood of detonation. Which could be quelled by dumping more fuel at the expense of power. Hence going richer than 11.5.

It seems clear that this is misguided, and that I could probably squeeze a bit more power out of my current tune by leaning it out a bit since it dips into the high tens at 20psi

9:1 pistons, exxon 93., I have enough confidence i he tuner to believe it is not detonation, especially when looking at the enrichment activity going on on my log at the same time.

Thanks for all the help everyone. Keep it coming.

yeah looks to me like you can for sure get more hp out of the current tune. good luck man.

the addition of extra fuel can only cool the charge so much, slow the burn so much, and lower peak pressure so much. after that it's just going to end up coming out raw out of your exhaust and washing down your cylinders.

Alright, I know I'm being a big titty baby here......

In a perfect world the afr would go to 11.5 and stay. How much leeway is there if there were a lean spike with afr?

it depends on how long it would lean spike and what your timing for that particular cell is at.

anything over 12 in boost on pump gas is asking for trouble

dude i run 12.5 at 17 psi and do alright most of the people on here that make apreciable power run mid 11's atlaest man up and give it a shot. Your fuel system is duel feed with a walboro 190 right? the pump is fairly new? the injectors are clean and fairlynew as well? What the hell else is gonna fail on you?

If you did blow a fuel line etc, then not only would your motor fuel cut before it self destructed but you would have to worry about an impending fireball as well.