Originally Posted by blackndecker

Ughhhh.....this thread always makes me envy the GD crowd.

Originally Posted by blackndecker

Ughhhh.....this thread always makes me envy the GD crowd.

Originally Posted by Lyon[Nightroad]

I'm curious why you recommend the c30-74 over the c15-60? Wouldn't the larger unit be harder to mount, create more parasitic drag below 180bhp, and be more inefficient until you start moving to the limits of the c16-60 at >~190 bhp? Or is this one of those things that would vary depending on my goals. I read corky bell's maximum boost but I still fail to grasp some things.

Originally Posted by DiamondStarMonsters

Well with the release of Bisimoto's CR-Z Turbo Hybrid and what little data I have been able get from the mods and figures/videos posted I am thinking about going far beyond my initial 180-200whp goals...

So in taking a break from studying this evening I was doing a little research on my plans for a turbo L15A and found some interesting stuff..

Before going further, unless you can already read or have a rough understanding of compressor maps and how different turbine wheels and housings can affect what part of these maps you will be able to use... I would read these links (in this order):

Stealth 316 - Turbocharger Compressor Flow Maps

TurboByGarrett.com - Turbo Tech101

TurboByGarrett.com - Turbo Tech102

TurboByGarrett.com - Turbo Tech103

The last one in particular is what I will be dealing with.

I have others that go more technical but that is a fantastic place to get a basic understanding of what I will be talking about..

So a Pressure Ratio of 2 on these maps is 14.7psi boost pressure. 3.0 is 29.4psi boost.






Garrett uses pounds per minute on their maps, which can be very roughly translated as 1lb/min = 8-9whp depending on BSFC, as discussed in the links above.


This first one is from a Garret Honeywell GT2554R which seems to be the turbo EVERY kit for the GDs and all of the alleged developing kits for the GEs has been using, and at only 5-10psi. Which you can see why they run out of steam so soon, especially when some GT25s leave even the 60% efficiency islands at 10psi at ~20lbs/min.

Bear in mind the turbine side is also affecting the compressor map, though it is rare you will actually see a turbine flow map I have some for you, which will also put in perspective the size of the 59mm Compressor Inducer (Borg Warner S259ETT, similar to the S258ETT) turbo I have on my Laser, which is between a GT3782R and a GT4088R when you compare both the Turbine and Compressor sides.

When people talk about 50-Trims.. that should tip you off that they have no clue what they are talking about. Because unless we know which Compressor or Turbine wheel and which housing he is using that information is useless Fast'N'Furious ricer non-sense.


I am of the opinion there are better options. Some of which are cheaper. Lets look at a few of the common street turbo options anyone with a GT25/28 could bolt in..


The HKS/T1R turbo that comes in your kits:

GT2554R :
Compressor Wheel Inducer 42mm/Exducer 54.3mm

Turbine Wheel Exducer 53.0mm




GT2560R:

Compressor Wheel Inducer 46.5mm/Exducer 60mm

Turbine Wheel Exducer 53.0mm



GT2854R
Compressor Wheel Inducer 42.0mm/Exducer 54.3mm



Turbine Wheel Exducer 53.8mm



Now note the difference in airflow and efficiency created by the 5mm larger inducer on the GT2860 compressor


GT2860RS
Compressor Wheel Inducer 47.2mm/Exducer Wheel 60mm

Turbine Wheel Exducer 53.8mm

This last turbine map illustrates the effect on flow through the engine between different size turbine housings, the red line being a .86A/R vs a 0.64 A/R on the same 53.8mm Turbine Wheel Exducer.

All this was to illustrate the effects of:

1.) Different turbine wheels in the same size turbine housing attached to the same size compressor wheel. Example: GT2554R v GT2854R

They both flow the roughly same amount of air at the same boost and efficiency. This is because the only difference being a slight increase of the turbine wheel (0.8mm) creates only marginal gains, if everything else remains the same.

2.) Different compressor wheels attached to the same turbine wheel in the same turbine housing. Example: GT2554R v GT2560

Using the same exact 53.0mm turbine in the same exact housing the GT2554R's 42.0mm Inducer/54.3mm compressor Inducer can flow about 28lbs/minute max efficiently. Versus the GT2560R's 46.5mm/60.0mm Compressor flowing about ~34lbs/min max.

The only changes being to the compressor wheel and a bigger air inlet (46.5mm inducer vs. 42.0mm)

3.) Different turbine housings attached to the same turbine wheel and the same compressor wheel. Example GT2860RS 0.64 A/R vs. 0.86 A/R Turbine housing.

The compressor maps only tell us part of the story. While the compressor may show it can push 37lbs/min, but because of the turbine combination it may only flow 31lbs/min in the 0.64 A/R Turbine housing using a 53.8mm turbine wheel and remain efficient.

But in a larger 0.86 A/R Turbine housing on the same 53.8mm turbine wheel it can flow the full 37lbs/min. So a 6lb/min gain changing only the housing that bolts the turbo to the engine.

In this example just by swapping to a larger, slightly laggier, turbine housing you can pick up ~40whp at the same boost.

Think of it like blowing through a coffee stirrer vs a garden house less pressure required but more airflow overall.


So now a real quick way to know what you are looking at when comparing maps now that you have the concepts discussed in the links I posted above:

Find say 5psi, 10 psi or 15psi (2.0 Pressure ratio) on these maps, draw a horizontal line and then draw a vertical line where on that farthest right outside island how. That is how much airflow that turbo will flow "efficiently" on that much boost.

You can see a whole bunch more Compressor maps from several companies like Garrett or MHI on that Stealth316.com link which should help you choose a good match for your project and goals!

Hopefully other DIY guys can find this useful and if anyone has any questions just ask, or PM me.

If anyone is curious, I would personally use a GT2860RS in at least 0.86A/R Turbine housing as the very smallest I would bother putting on an L15A for the money involved.

This is why I am using a 34lb/min Mitsu 14B turbo to start. because it has a large enough turbine side to flow all 34lbs/min while still spooling very quickly for it's size.

Remember, the 533whp L15A in Bisimoto's CR-Z turbo is using a Slightly larger turbo than the one I have on my 2.0L.

So if they can spool a freaking 64mm Inducer in a GT4088R on a tiny little L15A, You will have no problems daily driving a GT28xxR or larger. Here's how they do it:


GT4088R
Compressor Wheel Inducer 63.5mm/Exducer 88.0mm

Turbine Wheel Exducer 77.0mm




But look at the difference in flow the 4 different A/R turbine housings make on the same turbine wheel. With the fastest spooling .85A/R being the most restrictive and least efficient, and the laggy 1.19A/R allowing the most flow for top end power.

My whole point in all of this is, do some research if you are going to go turbo, and match things properly to your goals/driving style.

Do not waste your money getting anything in the GT25R family or smaller if you are gonna DIY! (in terms of airflow)

GT28Rs and larger will still provide plenty of torque, same power at less boost which makes it more efficient on pump gas, which is good for longevity, fuel economy and performance on a high compression pump gas engine.

A 38-40/lb/min Mitsubishi "small" 16G would probably be about the perfect monster street/strip turbo for our 1.5L's.

I am not saying everyone should go out and start buying giant GT35Rs or even (kinda) large 16Gs for their Fits, but there are alternatives!

Originally Posted by DiamondStarMonsters

Yes it is bulkier, and it will create more drag, depending on the pulley, but it is not necessarily inefficient below 180bhp (~19-20lbs/min airflow)

Now before reading further you may want to run to the john and grab a snack, this is a post from my tech thread. Note: a belt/gear driven centrifugal compressor's map is going to be different from that of an exhaust driven centrifugal compressor, but the concepts in terms of flow and efficiency are very similar.

The information in my post below, when compared with a list of Garret-Honeywell compressors and their recommended mate in engine displacement for given compressor/turbine configurations (The notes in the far right column like "1.4L-2.5L" or "2.0L-6.0L") should pretty thoroughly explain why I occasionally am harsh about the 24-25lb/min GT2554R compressor used in most GD turbo kits, and why I am using a 34lb/min MHI 14B compressor in stead..

So note that the turbine maps, and the different housings with different flow lines are similar in concept to different sized pulleys in the sense that they are the limit to flow and boost.

Hang on its gonna be a bumpy ride!



Now for scale and references of what I am babbling with compare sizes on this chart and look at what they recommend to use them on but keep in mind those are rough figures, a couple hundred cc either way doesn't really make or break a turbo unless it was a specific combination of parts, like a specialty OE turbo which are sometimes not very good on other applications. Schwitzer Airwerks K03/K04s like you see on VWs/Audis come to mind.



In closing, for the same reasons I am going to use the 14B turbo, which is a ~430cfm centrifugal compressor, so if I had the intent or funding, Iwould go with a 450cfm centrifugal compressor.

More air, less boost but no real lag to worry about since it is attached to the crank.

This compressor map for the GT2860RS


Shows 36-37lbs/min is about the most this will efficiently flow, and it does that at almost exactly 14.7psi or 1Bar Boost, which you can see if you draw a line the C30's map is likely comparable to this but I am still looking for the actual Rotrex specs. So you can see that 30-31lb/min or ~280whp on a fwd manual @ only 7.x psi boost is pretty appealing.

So depending on whether or not our stock fuel pumps can flow well enough (or if they have a pressure release valve) you could bump base fuel pressure up to 50-55psi using an adjustable fuel pressure regulator, and that would allow you to deliver enough fuel to get away with only tiny little RDX 440cc/min injectors.

So a bracket, belt, fuel pressure regulator, injectors, UEGO/EGT, supercharger, piping/couplers, intercooler and a tuning device is all you need to DIY.

Before anyone says "Thats way too big" look at that Garrett table.

Look lower ... lower.. They consider the basketball sized GT4708R Compressor with a 1.39A/R T6 Turbine housing a feasible turbo for a 2.0L application going all the way up to 10.0L. That is a 1400hp compressor

Not that it would be an awesome street setup, but that is not the point.. it is to suggest there is flexibility depending on your setup and goals.

Bisimoto's "tiny" GT4088R is only good for 700HP for comparison.

The Borg Warner S259 I just put on my Laser is just in between a GT37 and a GT40 and has proven to be a lot of fun, The 14B is the turbo I used to break in the built 2.0L currently in the Laser, and made a little more than 320whp and 350lb-ft spiking to 21psi @ 2900rpm in 3rd and holding 18psi to redline.