Sup ladies,

After not playing with my car for a while I've been bitten by the boost bug once again. I'm considering finally doing a sleeved block for my D16 setup and also getting around to ditching my stock IM and TB in favor of something like a Skunk2 or Edelbrock setup.

Currently I have an 18G on roughly 20psi and was wondering if this turbo has some more power in it, say at 23-25psi. This dyno to me, looks like it's pretty much out of breath but then again, I'm not too proficient in reading dyno's.

 

Do you have a graph with a boost plot overlayed? To me, it looks like when you hit ~53-5500rpm and VTEC kicks over, you actually lose power slightly which says to me that you're starting to hit a wall. I wonder if it didnt drop boost pressure slightly. Unless it isn't hitting full boost til ~5k, in which case that little trough would be the wastegate opening

 

hmmm....this is the only graph I have, the only other thing I possess is the tune itself which was done on an s300, would anything in there that I can screen shot give us any more clues as to what's up?

I suppose it's worth mentioning that this is on an internal wastegate, however I use one of these:

 

You could always do a data log, plot rpm vs boost for a good pull.

 

Back when I was looking at an 18g, I seem to remember people saying they didn't really "shine" until 18-20 PSI, and you could push them to ~24 before they stopped being useful. This is just from memory though, so my numbers might be off.

 

you're at the limit of that turbo... the turbosmart actuator was a good move as the one included with the kit sucked if trying to make higher boost pressure.

but really you've found the limit of the compressor wheel... the turbine wheel (gt28) is also about at its limit, which is around 350ish.

you could always take your current 18g and modify it. There's a few different ways this could go...

1. Billet compressor wheel -

- stay 18g: I know where a billet 18g wheel is that has a taller inducer blade height (5mm taller, same hub height), has a narrower hub profile as well as thinner blades (more blade surface area = higher flow capacity), as well as being extended tip. Wheel keeps the 6+6 blade arrangement. This is a direct drop in wheel, no machining of housings. The wheel weighs slightly less than the cast wheel so there would be a minor decrease in spool times.

18G Compressor Wheel (to compare)
- Inducer Diameter : 50.5mm
- Exducer Diameter : 68 mm

This could probably get you close to 350 but you'd then be limited by the turbine wheel. If you think you're experiencing surge anywhere at low rpm (due to boost pressure) you can get a direct replacement ported shroud (anti surge) 18g compressor housing.

- Go to a larger 20g wheel: (cast or billet) *would require machining of compressor housing or buying pre-machined housing (readily available and probably cheaper)*

20G Compressor Wheel
- Inducer Diameter : 52.5mm
- Exducer Diameter : 68 mm

The standard 20g wheel will flow a maximum of 700CFM or 56.49lb/min. You won't be able to get near the upper limit using this wheel WITHOUT going to a larger turbine wheel. You'll make more than you are now but it's hard to say what the turbine wheel will limit you to.

There's also a billet version available in either a standard 6+6 design or an 11 single bladed GTX style wheel. Both are extended tip, taller inducer blade height, and slim hub.

Pre-machined compressor housings are readily available for the 20g wheel that will fit your current CHRA. They start at about 100 dollars and you can get multiple styles... 2.5" inlet, 3" inlet (like your current one), 3" and 4" ported shroud (anti surge)

2. Larger turbine wheel (with or without billet wheel) - This would reduce pre-turbine backpressure as well as allow a higher rate of exhaust flow through the turbine wheel. This would result in a slightly slower response time but would make slightly more top end power (there's always a trade-off).

Stock TD05 (to compare)
- Inducer: 55.8 mm / 2.19 inch
- Exducer: 49.1 mm / 1.93 inch
- Turbine Shaft OD: 9 mm / 0.35 inch
- No. of Blades : 12

You could also go to a 9 bladed td05h wheel. Slightly higher flow limit, also weighs less than the 12 bladed wheel so it theoretically should respond faster. No machining needed

TD06H
- Inducer: 67.2 mm / 2.64 inch
- Exducer: 58.8 mm / 2.31 inch
- Turbine Shaft OD: 9 mm / 0.35 inch
- No. of Blades : 12 (available in 11 and 9 bladed versions as well)

TD06SL2 *requires machining of turbine housing, or buying pre-machined housing*
- Inducer: 61 mm / 2.40 inch
- Exducer: 54 mm / 2.13 inch
- Turbine Shaft OD: 9 mm / 0.35 inch
- No. of Blades : 11 (also available in a 9 bladed version as well)

You can buy direct replacement t25 internally wastegated turbine housings pre-machined for the larger wheels for 189 plus shipping.

Or go to a garrett gt(x)28 series turbo or something similar and let me buy the 18g lol

 

Wow man, that was quite a response and I really appreciate it, seriously.

So bottom line, let's say you were me..what route would you take? It seems like you've really got this 18G all figured out.

Side note, do you think I'd see significant gains/differences with an aftermarket TB and IM? Or am I better off allocating those funds to those sweet new 15x8 RPF1's?

 

With something like a Skunk2 pro series you'd see moderate gains almost everywhere with the majority being in the midrange. Assuming you went with a 70mm tb (phearable.net has a nice 69 or 79 dollar cast 68/70mm) and ported the manifold for the larger butterfly you *might* see around 15hp peak gains but I'm just ***-u-m(e)-ing.

It all depends on the tune and what you have left as far as fuel (chemical power limit) and the turbo (physical air flow limit) but I have a feeling that 350hp is going to be a pretty hard power ceiling with the td05h turbine wheel.

As far as what to do with the turbo it all depends on budget. You can buy a pre-built CHRA with a standard billet wheel (no extended tip and all the other things I mentioned) for around 550-600 dollars minus housings (figure around 300 for those with shipping) or if you're good with tools and basic turbo knowledge you can build your own.

The main problem with this route is your current CHRA will only fit an 18g exducer and won't fit a larger wheel without having the compressor side backplate machined for a larger exducer. Cost varies by shop since a CNC machine is mandatory, or you can buy a new CHRA machined for a larger compressor and/or turbine wheel for 149.

As far as other parts here's the cost.

Fancy billet wheel 149-159
Bigger turbine wheel 109-200
Turbine housing 189
Compressor housing 100-149
Rebuild kit 59
Billet "bullet"shaft nut 10
(Helps smooth out airflow into compressor)
Balancing 80-100

Now you can assemble it yourself if you feel comfortable. However when I talked to PureTurbo about balancing some of the turbos I'm upgrading with bigger wheels, billet wheels, etc they said if I pay for the vsr balancing and ship them all of the parts they would assemble it for free. Wouldn't hurt to call them and ask. Your Turbosmart actuator would swap over.

However as you can see this isn't exactly cheap. While you would have what is in effect a purely custom turbo you're still journal bearing and you're still using old technology. While the billet wheel has been updated with modern technology and the turbine wheel, assuming you go 9 blade, has been as well.

Will it make more power? Sure
Is it worth the cost? Debatable.

You could sell the 18g and put the money towards a used/new gt or gtx turbo. You can get the gt(x)28 and 30 series turbos with t25/5 bolt turbine housings. Your current actuator should swap over as well with little to no work.

Or you can get a turbo from TheShodan in the same turbine housing or go with something like an efr7163 (possibly my most favorite turbo lol) in a t25/internal wastegate but you'd need a new downpipe. The 7163 flows a max of 60lb/min (hard to get there) but therea no reason you couldn't make 500 with the right motor and fuel. Not to mention the titanium aluminide mixed flow turbine wheel makes the turbo hyper responsive.. on sti's it only spools 300-400rpm slower than the stock turbo.

staying with the td05h turbine wheel starts you out around 350-400 dollars, if you stay 18g then getting a ported shroud compressor housing would be a good idea due to the high boost pressures you're running. The inherent response of the turbo means you should be getting some surge at lower rpm/high load... going with a larger turbine wheel puts you around a maximum of 1015. This doesn't take into account any shipping charges though. So by the time do you ***** out with the 18g you could spend up to 500 more dollars and go gt(x) or efr and get even better results

 

That turbo isn't completely out of breath, it really holds torque well. DSM people push those turbos to & past the point where boost drops near redline.

Unless you make the whole package flow like crazy & drop the gearing to use the extra RPM, a larger turbo won't make you much faster. Even if more boost with the 18g doesn't raise peak HP, it will bolster your mid-range which can make you faster. A bigger turbo tends to drop out of boost more between shifts, which can make it's 75HP gain useless. I suggest you optimize what you can with a better intake and mild head work (bowl blending & performance valve cut), that way you extend the powerband rather than just move it.

 

the greddy 18g and mhi 18g use different turbine wheels.

The greddy 18g uses a garrett gt28 turbine wheel and turbine housing. They just call it a td05h-18g due to the fact that the compressor wheel belongs to that family of turbos.

The MHI 18g uses anything from a td05 to a td06h turbine wheel, all of which are larger than the gt28 wheel used on the Greddy unit. So yes the MHI unit will have a higher power ceiling due to the larger turbine wheel.

The turbine wheel is what limits the power on the Greddy unit, the MHI turbine wheels can flow significantly more before reaching their flow limits