Ok so I have a greddy Kit and Hallman Manual boost controller. I am having a problem holding 8 psi all the way to redline. I can find no boost leaks and when I open up my manual boost controller all the way the kit holds the stock 4.5 no problem. When raised higher to 8 its drops down to 6psi between 5000-6000 rpm. My last boost controller (Blox) did the same thing before it took a complete crap.

Any thoughts on what it could be? I have increases exhaust size exhaust from downpipe all the way back. And my wastegate spring arm has been tightened all the way. Thinking maybe timing but i dont know if making sure its at OEM timing is the best set up and I wont be able to get a tune for better adjustment till the spring (running wideband to monitor A/F +310 injectors with increased boost). Car idles and 15.0 and pulls hard to low 11s. No stuttering on pulls either just a lost of boost. Even ran the car with no filter how it was clogged somehow.....

Really need some help from others with turbo fits or have knowledge in this subject.

 

Well here is something to consider... boost is merely the amount of air that you are not flowing. Boost is created by restriction on the intake side.

Sometimes when boost drops as rpm increases it is because the engine is able to accept the air you are pumping through more easily.

If boost drops at upper rpm but airflow stay the same or increases this is a good thing.

Other times it means you have a clog somewhere like a collapsed flex section, clogged cat or the downpipe and turbine housing are too restrictive.. or you have a pre-turbine exhaust leak like a crack in the manifold or turbine housing.

Another option is that the engine is choking on the turbo and trying to flow more than the turbo can provide at that boost. So boost would fall as well as airflow.. this is bad

I would first bet that some component of your exhaust is too restrictive or has a leak. My next guess is that the GT2554R that came with your turbo kit is too small.

Or both.

Your timing does not affect airflow, timing is simply when spark is introduced.

Edit: Upon re-thinking this you might just be blowing your wastegate open. If you are careful and gradual with the throttle wire the wastegate shut and use the throttle to limit boost and see if a completely sealed wastegate will let you hold 8psi to redline.

and don't let the throttle snap shut find a spot where you can gradually get on the gas and slowly let off. With the gate stuck shut, boost will spike very fast on such a small turbine with a tiny housing.

 

currently running 2 1/4 from downpipe back. High flow cat, small resonator and Ap1 muffler (set this up before turbo kit). I would not think it would effect 2-3 psi after only making 8 as it is. Its weird because when I cranked it up to 10 for more tries it only dropped down to 8-7. I will call greddy and hope they wont tell me they actually sell a turbo kit that cant put on more that 170 whp....

 

While your exhaust is on the small side, that is enough pipe diameter for 225whp.

The turbine housing is very restrictive on the greddy kit. In addition to it being a non-segregated 5-bolt discharge, the housing (volute) itself is very small, and it is also only about 65% efficient at best when it comes to converting drive energy into boost.



And even at that 65% efficiency you are choking at about 16lbs/min which is about enough air for 150whp on a good tune. You are pretty close to choking at 8psi already (1.5 pressure ratio, or 0.5 bar boost)

Not only that but the compressor is on the small side for a 1.5L especially one with such high VE up top like the L15A.

This is the compressor map for your turbo, which is more a show of potential and not accounting for the turbine map, which greatly affects what parts of the compressor map you can actually use:


This is a T25 for comparison:

 

this is the link to the turbo kit, includes their dyno chart at up to 8 psi aswell

Welcome to the official GReddy USA blog: Bolt-on Turbo Kit for Honda Fit

Turbo size is TF035HL-14GK, same on the Scion xB kit

 

8psi and 150whp is about what I would expect on a T25/GT25R which is what everybody else is using.

Greddy uses MHI (Mitsu) internals with their housings. I had a bit of a brainfart.. sorry its late and its been a long day for some reason I was convinced that the Greddy kit was like the T1R/HKS kits.. and used a Garrett turbo.

Your kit is using a Mitsu 14G compressor wheel inside of a Greddy compressor housing attached to a Mitsu TF035HL turbine wheel inside a 6cm2 Greddy turbine housing.

The 14G is a roughly 35lb/min wheel and should easily flow enough at 8psi on a 1.5L to hold boost to redline on a 6cm2 (volute, critical area) turbine even with the TF035HL wheel and the non-segregated housing..

8psi on a 14G compressor attached to a 6cm2 turbine housing should move about 18lbs/min or enough for almost 180whp vs 150whp like the T25.

There is definitely some sort of leak or restriction in your setup.

Greddy uses MHI (Mitsu) parts. The below map is for the 14G but attached to the TD05H turbine, so the compressor (intake side) is the same but you have a 6cm2 "open" housing with TF035HL style turbine (exhaust side):




Which has a non-segregated wastegate, basically both the turbine and wastegate have to breathe through one open odd shaped hole. This creates turbulence, and boost creep on smaller turbos like the GT2554R I was babbling about earlier.. This is the downpipe side:



Instead of the 6cm2 TD05H style turbine with a 4 bolt inlet and a segregated wastegate:


Which can better control boost and flow more exhaust through the same size turbine wheel. This is because it is re-introduced later into the exhaust stream after it has had a chance to organize a bit and smooth out:


Or you can dump the wastegate to atmosphere which in addition to shooting flame out at full boost and making a good deal of noise also allows your existing exhaust pipe to act like a larger pipe.

Because of all the exhaust that is allowed to bypass to atmosphere through the dump tube freeing up space for the stuff exiting the turbine. This not only increases spool but helps boost control and allows for greater pump gas efficiency!:



So the compressor wheel can flow what map for the 14G below shows, and that turbine side basically determines what parts of the map you use and when! So does the weather, altitude, intercooler and fuel system among other items.

You can run across different style turbine housing attached to the same exact turbine wheel and compressor wheel/housing! Of nearly the exact same size.

To further complicate things the names like "TD05H" is actually the name of the turbine wheel.

A "TF035HL" - "14GK" is a Trust Greddy modified assembled turbo made of Mitsubishi "14" family "G" trim "K" spec compressor wheel inside a Greddy compressor housing attached to a "TF035HL" Mitsu Turbine wheel in a Greddy Turbine Housing.

I tried to bold the 4 different full component names to help separate them out of that word salad.. As those are what most affects actual performance.

It is important to note that the map for the turbine and the map for the compressor are done independently, so you have to take the pairing of a particular wheel and housing to figure out what they do by them selves and then use that to figure out what they do when you attach a turbine wheel/housing pair and a compressor wheel/housing pair.

In gasoline engines the turbine side tends to be the restricting side, meaning that a given compressor side can work on a wide variety of engine sizes and how effective the compressor will be is then determined by the turbine side. This is because for a relatively small exhaust volume, there is a lot of energy that can be used to drive a large compressor because the exhaust is so hot.

So by itself this is what the 14G flows on a 1.5L engine, never mind the TD05H part because that is the turbine side and does not affect the map below:

(This map belongs to stealth316.com Though it says 2.972L displacement, this is for a twin-turbo 3.0L V6 so the demand lines on the map is actually for only 1.5L worth of engine)



Sorry for the essay I felt I needed to clear that up a bit. So if there were no leaks or restrictions you should really be having issues with too much boost on that turbo, not too little. In any event try the things I suggested in the previous posts and let us know what you find!

You should be able to solve this by checking for:

1.) Post-turbo boost leak on the intake side
2.) Exhaust leak where cylinder head and manifold meet
3.) Exhaust leak where the manifold and turbo meet
4.) Restriction from collapsed flex section
5.) Restriction from clogged catalytic converter
6.) Wastegate blowing open
7.) Restriction from excessive backpressure/turbulence at the turbine

 

Is their a way to best test all of that? No tuning shop locally which is why i am waiting till spring to ride to one. I have zip tied all lines and checked couplers. Need a better way to test leaks that I or say a local autozone/dealership can do. Thanks for all your help tho

 

I noticed today going home from work as I went through 2nd and 3rd my boost maxed at 6 psi all the way through the band at full throttle. Now when I went to 5th and gave it some gas (example going up a hill)it would be able to reach my 8psi that my controller is set at.

I am thinking this has more to do with the weather here. Its been very cold lately, average highs in the single digits and sometimes in the negative, Lows at night reach -20 before wind chill. I try to let my car warm up as much I can while i freeze in it before I drive off. With the temperature that cold will it effect springs in wastegate, BOV, or controller? Maybe freeze my intake filter to the point where it doesnt let alot of air through on high loads?

Just a thought, will to more test as its suppose to get to 40 by sat (thank god)

 

ok so I just got off the phone with greddy. They said I should upgrade to an electronic boost controller. They stated that manual boost controllers have a hard time holding boost of 2-3 psi at high RPMs. And what maybe happening its its actually set closer to 6psi than 8psi, so its spiking to at during rpm climb and then leveling out to 6 as it closer to redline.

Does this sound right?

 

You will have to make a boost leak tester for the intake and a similar device to test your exhaust tract.

Something like this boost leak tester I made from PVC piping and a compressor fitting cost me $40 and an hour at home depot:



The gauges on the item attached to it is a compression leak down tester which you don't need but I would advise renting or buying one for the purposes of these tests.

This is what it looks like attached to the intake side of the turbo:



You need to make one that attaches to the exhaust pipe to test for leaks.

Then when you establish there are no leaks on the exhaust you will need to unbolt the exhaust and inspect the catalytic converter for clogs, and if you have any mesh flex sections you will want to make sure the sleeve inside hasn't shrunk down to a pin hole which happens more often than you would believe.


You have a leak, there is more load generated in 5th gear, you spend more time at a given rpm so there is more work done on the turbine wheel over the same span of the rev range compared to 2nd and 3rd. You will notice you also spool faster in higher gears than lower gears.

This is why you were seeing only 6psi in 2nd and 3rd, but there was enough load generated by 5th that you could build 8psi, even with the leak.

Colder weather = denser charge should mean more boost occasionally on spikes, so that is not weird. Engine components don't really care about windchill, it is the ambient temperature that would effect them. You should not worry about the temperature affecting your springs/diaphragms especially if you are letting it warm up, which you should anyways. You want the oil warm before you mash the gas, always.

No that doesn't sound right at all. It sounds like they want you to spend a bundle of money on an EBC, and all you would have to do to demonstrate that they just fed you a line of crap is just to swap springs in your MBC.

I have had a Hallman Manual Boost controller in several cars, they are the bleed down type. The MBC, especially a Hallman, will not cause boost to fall of.

Like I said, if anything involved with the boost control system is failing you, it is your wastegate. Do not waste your money on an EBC.

You have a leak or a restriction in your system. My bet is that you either have a boost leak on the intake, an exhaust leak or a restriction in the exhaust system.

Possibly a combination of all 3.

Did you check for any vacuum or boost lines that have popped off? Any loose couplers on the intercooler piping? For any spots building black soot on the exhaust by joints.

And you can even see my Hallman MBC in this picture:

It's that red cylinder attached to the wastegate with a pink reference line.. I probably run more boost than anyone else on this forum so if the Hallman works for me, it will work for you.

In the summer when there is traction and a track to use it on I usually run between 35-38psi boost (weather permitting) on a cocktail of Methanol, Toluene and 93oct pump gas.

Edit: can you take some pictures of your setup for us? Maybe you have one of your boost lines attached to your source, BOV or wastegate configured incorrectly...

 

OK this is the overall set up.


Here we have the Hallman MBC and my boost gauge tap (blue). The bottom line goes to my wastegate, and my top/back line goes to turbo



Here is where my BOV is taped from and BOV



other pictures or turbo, wastegate, and oil lines, i know you cant see much but there is not much room back there lol

 

Ahhh I think we found part of your problem!




Those zip ties are a big no-no!

Get some little wormscrew clamps on any spot where you have a clip or a zip tie and go for a spin.

Also you want to clamp all of the lines and hoses in the system that see boost or vacuum.. including the BOV line and the lines on the boost controller and the PCV/Valve cover vent system!

Air will do its damnedest to escape under pressure, and even an incomprehensibly small hole can leak a lot of boost.

There still may be more to it than that, but that is a great place to start! I still think you may have some exhaust leaks or restrictions based on what youve told me upthread!

 

Hey man you ever figure out the problem? I have a greddy kit aswell and I see some tappering with my manual boost controller but not wastegate drop...