gospeed81

iTrader: (51)

I want a better powerband.


I need advice on the best little upgrade I can make to get a little more out of my mini-turbo strapped to my mini-motor.

The IHI is seriously running out of breath at anything north of 10psi, and even at 10psi torque drops of at high revs, and my IATs get up to 125*.

I've got a little money to spend, but not a lot, and want to keep my nice BEGi setup if I can. Everything bolts together well, and is high quality...which is why I bought it. I definitely can't afford another manifold or downpipe, which confines me to my current turbine housing.

I might consider hacking up FMIC setup, but would have to be some serious gains since I'd have to pay and fab a lot.


Here are a few options:


1. WATER INJECTION ~$360

I looked into this a while back...but recently sold the few parts I had. I would be looking at the progressive Devil's Own kit...but that IS a lot of ching-dow.

I would mainly aim to lower IATs since my compressor is just blowing hot air on the right side of the map. Timing isn't much of a concern since I have plenty of mid-range power which is where I'd be able to add in a few degrees. Top part of my map is already pretty well advanced, and I still feel like I'm running out of steam up there.

EDIT: I'm also considering just putting the nozzle in front of the compressor inlet to "move" my map over to the right a little.


2. ADJUSTABLE CAM GEAR ~$100

Have heard of folks retarding the intake gear a tooth, or using adjustables up to 12degrees retarded to reduce overlap...and pick up some top end. This is really appealing to me...but haven't found too many success stories that apply to my situation, much less good write-ups outside of y8s' tale of two turbos.

3. LARGER COMPRESSOR ~$200 +IC = $400

Upgrades are almost completely limited to the "t-bird mod" which uses the turbo coupe's compressor wheel and housing. I *KNOW* this is what I really need to do...but there's a lot involved.

I would have to balance the assembly, get a bigger IC, redo piping, maybe look at bigger injectors, and end up bending rods anyways since that monster would put me closer to 250whp.

If I do this I might as well start over.

I'm not necessarily looking for a lot more power, although that's always welcome...I just want it to pull up top like it pulls down low. I dig the non-existent lag, but feel like I should be shifting at 5500rpm.

4. LARGER INTERCOOLER ~$200

I'm not sure this would help a lot since I've got a pretty good BEGi bar and plate design. My compressor flow map is really the problem.


ANY and ALL help appreciated.

I'm finally getting the suspension, brakes interior and everything else where they suit me...now I wanna revisit the powerband.

Thanks,

-Damon


PS. I'm already working on a COPS setup.

sixshooter

iTrader: (12)

You know it's a turbine problem, so screwing with the cams won't give you a better comp map or reduce outlet temp. What are your IATs?

gospeed81

iTrader: (51)

Here is spark table and a graph of a multiple gear pull with IATs at ~9psi.


EDIT:

Generally I'll see my IATs go from near ambient to ~120-125* in a single pull.

levnubhin

iTrader: (30)

I don't know what flanges that turbo uses but maybe you can get a bigger china charger.
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gospeed81

iTrader: (51)

I would do this in a heartbeat, but haven't seen any come up.

Seems that they're copying the more popular flanges first...and are just now making decent ones.

The few popular IHIs all have funky suby flanges on the hotside.

gospeed81

iTrader: (51)

In all honesty I'm happy with the power level. I expect to get a little more as I upgrade to COPS and 2.5" exhaust.

I just want it to keep pulling. I am honestly fine with the power "kicking" in and expected this when going turbo. Unfortunately I picked the turbo that fit my budget and not my needs...so now I'm paying.

I think I just want to move the powerband a little, or easily pick up more power up top. I'm definitely fine between 3-5Krpm.

TurboTim

iTrader: (9)

can you make a 1/2 inch adapter plate to go from your bolt pattern to another more popular version?

gospeed81

iTrader: (51)

I had given this some thought...and have access to a waterjet or mills to make it work.

I'm pretty sure it will throw off the nearly perfect job Corky did ~12yrs ago of making this downpipe and manifold line up perfectly. Both flanges would need adapters, or I'd have to fabricate a new downpipe.

At that point I might as well start over...and if I start over it will be with a 1.8L...and if I get a 1.8L I might as well build it....

Slippery slope I'm trying to avoid.

magnamx-5

iTrader: (7)

WI can be done for less than 200 bucks man at your lvl you do not need a progressive system in the least man. Simple =win=cheap=effective=reliable. im not familiar with the rb5 lemme see what i can find

magnamx-5

iTrader: (7)

looks to me like you still have a good bit of room Squirrel Performance WI could wake your setup up wich one are you running the 3991 or the 4219

gospeed81

iTrader: (51)

Mine is the 3911 (tiny little bastard)...the 4219 is the Thunderbird turbo, what I would like to upgrade to.



Damn mods.

Stein

iTrader: (46)

lulz

sixshooter

iTrader: (12)

Your exhaust is how much smaller than 2.5in? Opening that up might either reduce the boost pressure and cause your turbo some relief and/or allow a few more cubic footsies of air through your motah.

gospeed81

iTrader: (51)

I'm running stock exhaust with a hollowed out cat right now.

I understand it's still a restriction, which is why I've got a dynomax sitting under it right now (was sold to me as a 3" in/out...turns out it's 2.5"...will have to live with it).

Either way I'm still falling way off the efficiency map at higher boost/revs. See the attached plot of the MAX I'm comfortable running. That second to last dot is 6000rpm, the one after it is 6500, which puts 7000(or 7200) off the chart.

The falloff is really bad now, so I'd say it's still gonna be at least bad even after exhaust and COPS.


Maybe I should rephrase my question as:


What's the best way to combat poor compressor efficiency in the top end?

sixshooter

iTrader: (12)

Yep. Boost won't help you now. You are out of flow. Retarding cam timing will exacerbate the problem because you will move the cam's powerband further up the RPM range where you have no turbo. It would make things worse. Everything needs to be optimized for your operating range. I would still run larger than stock exhaust piping as soon as possible. You will likely pick up some healthy torque in the range that you are operating in currently. You need a bigger pipe, not just muffler.

gospeed81

iTrader: (51)

Upgrading pipe as well.


I thought retarding the intake cam would improve the volumetric efficiency up top...allowing me to get more power out of what little flow is up there.

gospeed81

iTrader: (51)

I ordered an adjustable cam gear yesterday.

I was already putting in an order with Moss, and another part I needed was free ($30 value) if I got over $125. That meant after shipping and parts savings I've probably got a $70 cam gear. It's the cheapest option on the list...and worth the gamble.


If nothing else it will give me something else to play with on the dyno. I plan to have as many upgrades in place before I pay for dyno time. I would like to retard a degree or two on the street...datalog for it...and then see if retarding anymore nets more top end area under the curve in consecutive pulls.


Since this was so cheap I'm definitely open to other ideas that would help improve my top end efficiency.

On WI...if I do anything at all...I'm going with a progressive kit. I know I can do a non-progressive (in reality reverse progressive), but I see more value in the better kit. I nearly had everything needed for a single stage DIY non-progressive setup, and I never felt good about putting it on the car and trying to tune for it.


My real problem with my power band is that it's no longer Miata-like. The stock 1.6L had little power, but pulled hard all the way to redline. I want this again.

hustler

iTrader: (6)

why is everyone on this forum obsessed with me?

levnubhin

iTrader: (30)

Because you're the ***** ******* man, didn't you know?
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sixshooter

iTrader: (12)

If you are going to play with the cam timing on the dyno, try advancing it four degrees, too. See what that does for peak torque numbers and how the curves shift around. A little empirical data would be great to have. BTW - did you see this thread regarding exhaust and turbine pressure differential?