LonnyEnds

Hello all I am currently running my GT28RS with a 15psi wastegate and it hasn't skipped a beat. I am looking to crank up the boost to a nice round 20psi but am not completely sure if it is possible.

If the turbo gurus could chime in, preferably with someone running this turbo at those levels that would be great.

The map for the turbo can be found here:

ATP TURBO - The Premiere Provider of Turbocharging Components

https://www.turbobygarrett.com/turbo...rgers/gt2860rs

Ive been using this airflow/pressure ratio calculator to help me plot:

Compressor Flow Map Calculator

I realise this level of boost would be pushing the limits of this turbo's efficiency range etc. However depending on VE (volumetric efficiency) the safety margin changes. I am running a B18B (Jdm) but have failed to find solid numbers on the VE. My rough calculations using HP, BSFC, Fuel flow etc give me ~95% VE which to me seems a bit high for a non-vtec Honda. (90% VE puts me just within the map)

If anyone has run this turbo at those levels please let me know. This is a DD that is run hard but not beat on. My setup is for midrange street driving and thus the time spent up @ 5000-6500 RPM in minimal so while I know the temps will have to be monitored closely and my tune spot on/conservative it appears that it should be just fine at these levels.

I do not need recommendations on switching turbos, tuning or any other parts I am simply looking for anecdotal evidence that these turbos can work at 20psi with a B18B. Just FYI I am using the .64 A/R turbine version and my power levels are right about 230 hp and tq to the wheels. (this is due to restrictive greddy downpipe, 2.5 inch exhaust and CAT)

Thanks so much for any help!

extremeracer

I don't have personal experience with a GT28RS on a B18B but just off the bat I'd say the 0.64 housing is going to restrict your performance. The SR20 guys have seen improved performance using the 0.86 housing vs the 0.64 with minimal trade off in response and that is on the low flowing SR20 head - your B18B head is bound to have higher flow rates and better combustion efficiency than the anemic SR20DE(T) and be tolerable to high backpressure (as Honda B, K, H and F series engines are by nature).

My advice, remove the restrictions in your setup (downpipe and turbine housing) and you'll make more power at the same boost level rather than forcing the turbo to work harder due to restrictions and creating more heat and detonation sensitivity.

My 2 cents

LonnyEnds

Thanks for the input, I realise how and where I could pick plenty of power however until this turbo or motor dies I am going to run with what I have. The main thing holding me back is for sure back pressure as the Greddy A/C compatible elbow and 2.5" exhaust make for a great street car but vastly restrict how much the engine can breathe. I just want to be clear that I will not be spending any money at all. I suppose the most valuable information on the theoretical side would be to know the VE of the B18B. Ideally someone with this turbo has anecdotal evidence as well. Even a 1psi reduction to 19psi would reduce the pressure ratio to a more comfortable level. Also if anyone could chime in how much of an effect of being @ 1000' above sea level and higher than standard temperature would have (density altitude) . Would this exacerbate the efficiency problem as the air would be less dense?

rice a roni

iTrader: (1)

Looks like at 15psi that you're already off the center island, but still at 75% and 20psi would take you to 72%. Now I'm not a guru or anything but I've read that staying over 70% is ideal.

I did 1.8*7200*90*2.36/5660 = (cfm)/14.27 for lb/min. Depending on what you use for VE and RPM it doesnt look too bad on paper.

LightningTeg

Dont overthink this, Just go for it and see what happens. Obviously the tune will have to change. If the turbo is out of breath the boost will fall higher into RPM

On my B18B, I ran my GT2560R to 23lbs and it would fall to 19lbs by redline. Made 300whp/300trq

LightningTeg

All of this. My old setup with the smaller GT2560r. Ended up making a 3" elbow to replace the cast greddy crap and it helped a ton.

LonnyEnds

Ok cool thanks guys I was coming to the same conclusions. I've thought a ton about freeing up the elbow, downpipe and exhaust but it's just not in the books for now. I was hoping you'd chime in lightning as your old builds were very similar its great to see your car at the next level now.

I guess my main concern was that I keep reading people claim B18s (mainly B18Cs) are over 100% VE. When up at 20psi the difference between 90 and 95 VE at the top of my rev range puts my point just on or outside of the map.

Basically the turbo might simply drop down to a lower boost level and IATs will rapidly increase if it is off the map right?

On that train of thought is there a generally accepted max IAT that you would want to see? Or as long as there are nice rich AFRs (11:1) and enough timing pulled to prevent detonation high IATs are "safe" but obviously holding me back power wise.

I probably am over thinking it a bit but as I push the upper limits of the turbo I am also reducing that safety margin from knock.

Thanks again to all the more info the better.

LonnyEnds

Also lightningteg did you fab that elbow yourself? No chance you still have it kicking around I'm guessing?

LightningTeg

No my buddy made it for his greddy kit in college and sold it to me. Its long gone. It wasn't that well made, had to repair it a few times. Your best bet would be to find someone to make it for you.

LonnyEnds

Figured that would be the case haha nothing ventured nothing gained.

If anyone could chime in on IATs that would be great.

TheShodan

iTrader: (14)

You have to track those for yourself, unfortunately. Different intercooler types and sizes, intake manifold types, and their relative to their IAT sensors locations give different results. The efficient range is based upon their temperatures in comparison to ambient outside air temperatures ( taking into account humidity and barometric pressure when possible)

Also, your tuner will adjust timing and fuel trims based upon what those temperatures are accordingly, and will lower boost pressures to get maximum efficiency where needed.

LonnyEnds

Yes I will be watching IATs closely. I am actually my tuner that is what prompted me to ask if 20psi would be off the compressor map with a B18B. I understand that there are MANY factors that go into power/knock limitations of an engine and that everyone will be unique. I was just wondering if there was a general consensus on "above X degrees IAT there is barely any/no safety margin" I have to double check some datalogs but I am willing to bet at the track I have IATs above 130 degrees F. Am I wrong in thinking that higher IATs, even say at 200F+ can for the most part be offset by more retarded timing.

In the end law of diminishing returns and knock limitations of the fuel will decide how much boost/power I run. I am looking to street tune with a Det Can fuel maps at the turbo's max output, then put it on the dyno and bring timing in. I am guessing it will take less than 20psi to reach my 250-275whp goal however Id much rather have a safe tune up to 20-22psi in case of spikes etc.

gorillaglue#4

Are you using forged internals or are you bone stock? What size inter-cooler are you running? Im building out a LS motor for this turbo.

LonnyEnds

Yes bone stock internals B18B bought from a JDM parts company ($550CND) with "~65000km" although there is no proof of that so I am planning on doing timing belt soon. Can't remember the compression numbers but a leakdown test verified next to no losses. (Honestly probably around 2-3%) I was ecstatic about this as this was after my first season tuning and driving the car hard.

As for intercooler I got the largest precision one that would fit withour any trouble, I believe it is the "350hp" version. I am so glad I didn't cheap out on it as there are many other parts of my system that greatly contribute to intake temps.

As others have mentioned it all depends on your end power goals. For a mild, very drivable and awesome spooling characteristics build the GT28RS is hard to beat.
The more research I did on it the more times I saw it was a "fun" turbo and I'd wholly agree!

IMHO you could probably max this turbo and still not be in that territory of not NEEDING forged internals but of course they offer you that bit of knock protection. (Anyone correct me if wrong!)

It all comes down to the tune and mainly how aggressive the timing is. I'd happily leave 50hp on the table to have something reliable regardless of atmospheric conditions or something like a bad tank of gas. Not sure how cheap and plentiful B18s are around you but the complete longblock I bought was cheaper than just the machining would have cost.

GT28RS + LS Trans ftw

TheShodan

iTrader: (14)

Unfortunately, the Precision 350hp is a cheap out version. You were better off with even a Treadstone or Mishimoto 550hp at that point.
Most of these intercoolers you're seeing are rated at the crankshaft. So a 350hp intercooler is really more for 290whp or close to it, at maximum efficiency.

The Garrett 400hp core and Bell 400hp core is a bit different as they rate it more to the wheels not the crankshaft. They do cost a bit more.

If the balance of the two were possible, the CSF, Treadstone and Vibrant cores in over 500hp configurations would have been a better move for you with this turbocharger at these levels.
You were worried about IATs before.... With that Precision core, now you're really going to be paying attention.

Unlike with sizing turbochargers, it's always better to get a little larger than you think you need: Here's a writeup on Intercoolers found on the FI FAQs:

http://speedtrappconsulting.com/imag...tercoolers.pdf

LightningTeg

I never had an issue with my ebay intercoolers running the little GT28R past its efficiency. This was on 93 mind you.

TheShodan

iTrader: (14)

it still depends upon the core size. EBay is just
​​​​​​ a location to purchase

LonnyEnds

Oh my bad the precision was considered one of the best options 8 or so years ago I thought. Did your turbo go on you lightning or was it your motor/ just changed your setup?

So there is no general "don't go above X degrees IAT" and as long as there is no knock all is well?

LonnyEnds

I just double checked my saved datalogs from the track the highest IATs I've seen were 165F staging, by the top end it had come down to 140F.

LightningTeg

They were small.

scottcraft

Was that in your integra? That had to be a blast on the street!

LightningTeg

Oh yes it was! It was so responsive I would jump out on other boosted hondas making 100whp more and hold them off until higher mph. Great daily driver for sure.

LonnyEnds

Ok so an update:

Turns out the guy on ebay years ago that sold me the turbo was LYING, didn't sell me a GT28RS and actually have had a GT2560R (Garrett PN 466541-4). Needless to say the turbo ate its bearings at 20PSI after 4-5 runs down the track. lesson learned ALWAYS double check PN especially off ebay. So my "good deal" in reality was slightly below retail. So I have bolted my 18G back on for the time being but need to decide how to move forward. TBH now I want a GT28RS more than ever as it is a step up from the GT2560R. Now from what I am seeing the trims of the two turbines are different, so I am guessing that when they say, "Upgrade turbocharger for GT2554R (471171-3) and GT2560R (466541-1); turbine housing flanges are outline interchangeable" about the GT28RS that simply means it will be a bolt in replacement and not that the GT2560R turbine housing could be put onto a .64 AR GT28RS CHRA (430609-0230)

The answer doesn't seem as clear upon further investigation.

http://www.capa.com.au/pics/turbo_ga...dimensions.pdf

http://www.capa.com.au/pics/turbo_ga...dimensions.pdf

T25 Flanged Internally Gated Turbine Housing for GT25, GT28/GTX28, GTX29, GT30R-WG : atpturbo.com

According to those it looks like it might work? Doesn't seem to be different part numbers for each individual turbo. Would this mean the turbine housing on the GT2560R in fact does have room for the 1mm larger Inducer and 5mm larger Exducer? This would be great as buying a GT28RS CHRA and Compressor housing would be cheaper than a full turbo. But I am definitely leaning towards upgrading unless I can get the 2560R CHRA for cheap enough.

LightningTeg

Uh the turbo shouldn't have grenaded like that o_O. What was the oil feed situation like?

TheShodan

iTrader: (14)

That was actually the first thing on my mind as well. The other information was just moot. This needs to be addressed first.