GT28R stock twin turbo upgrade development and testing

**To purchase this turbo kit, you can BUY IT HERE!**

Hello everyone…testing is now done and results are below! Due to the clutter and sheer size of the thread on SupraForums (located HERE) regarding the exciting new GT28R stock twin system for the 1993-98 Toyota Supra Twin Turbo, I decided to start this page to keep track of our progress on the test vehicle as it progressed. If you have any questions, please post them in the SupraForums thread for now.

The peak numbers on a Mustang Dyno using 116 octane gasoline at 21.5psi were 520rwhp and 487rwtq with a VERY conservative air:fuel ratio. At 24psi they should make 550rwhp or so, however this would max out stock fuel injectors at a 100% duty cycle which I don’t recommend doing. These turbos will be ready to be sold on Monday, May 19, 2008. The price for the twin GT28R turbos and the installation kit (lines, fittings, hoses, etc) will be $3300 plus shipping. We have about 12 sets of core turbos to minimize your down time if you need them. If you buy a set of these GT28R turbos without sending in your stock core turbos first, there will be a $950 core charge that is fully refundable once we receive your stock cores back (must be returned within 30 days to be honored.)

First, let’s start off by noting some test data:
Installation and instruction touch-ups performed by Jared Pink from SpeedForSale, and the dyno tuning and write-up were performed by Jeremy Blackwell from SpeedForSale. Turbos developed by BNR Supercars. Turbo installation kit and idea facilitation by Stu Hagen.

Pictures of these turbos can be found BY CLICKING HERE. Also, here are the details and specifications of these twin GT28R turbos compared to the stock CT12B turbos:

The test vehicle’s information is as follows:
1997 Supra Twin Turbo (INFO and PICTURES HERE), 6-speed manual transmission, 86k miles, original engine with a recent compression test that yielded the following results: #1=165psi, 2=163, 3=168, 4=167, 5=168, 6=168. This car has been brought to us for parts and service for several years now, and it has been VERY well maintained! The owner cares more about keeping the car in top notch working order compared to adding more modifications. We have installed every modification on the car other than the coilovers, downpipe/exhaust, intake, and wheels. It is one of the more solid and problem free Supras with 80k+ miles I’ve seen…it’s a nice one! We just changed the Champion Race Plugs that we use on all Supras after having ~20,000 miles of use put on them, and they were still in good enough shape to reuse for a while longer with no miss (see pictures by CLICKING HERE.)

Modifications include
– RPS stage 2 clutch installed recently
– Blackwell E-TTC switch kit (allows the stock twin turbos to convert from sequential operation to parallel (true twin) operation with the flip of a switch mounted beside the traction control… INFO HERE)
– Autometer electronic boost gauge
– S4S cross drilled and slotted rotors with new OEM Toyota pads
– calipers painted black
– White Supra script on calipers
– S4S black Italian leather shifter boot
– Champion Race plugs gapped at 0.035" (much better than NGK in terms of gap size without missing and life span)
– TEIN coilovers
– Kinesis wheels
– downpipe
– 4" Ti cat-back exhaust
– Maxx Air box with K&N filter
– HKS Type S Front mount intercooler with T-bolt clamps
– carbon fiber upper radiator panel
– Greddy ProfecB Type-S boost controller
– Greddy BCC
– Blitz DDBOV on cold intercooler pipe and stock bypass valve on hot intercooler pipe
– Innovate Motorsports XD16/LC1 wideband combo

AT THIS POINT of the modifications list, the FIRST round of dyno testing was done. You can see the results below…

We then installed these parts:
– GT28R stock twin turbo upgrade kit
– Polished upper radiator hardpipe
– Mishimoto Radiator test car

AT THIS POINT of the modifications list, the SECOND round of dyno testing was done. You can see the results below…

We then installed the final items:
– MAP ECU
– HKS DLI

AT THIS POINT, the THIRD round of dyno testing was done. Results below…

FINALLY, the FOURTH and FINAL round of testing was done with 116 octane leaded gasoline. Results below…
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FIRST ROUND OF TESTING:
- April 9, 2008
– Results are from a Dynojet 248C with SAE Correction (NOTE: MAP ECU tuning will be done on a Dyno Dynamics load bearing dyno, but we used the DynoJet inertial dyno for the horsepower readings because they are ‘glory’ dynos and read higher horsepower numbers that most people are used to…)
– Conditions via Weather.com were 1:00pm eastern time, 70 degrees F, partly cloudy, 52% humidity, 30.19 in/hg and steady, 52 degree F dew point.
– 93 octane pump gas was used for these pulls
– The car was driven 45 minutes to the dyno, and the ONLY cool down time it had was while it was being strapped down to the dyno! We allowed 1-2 minutes cool down time (with the car still running) between pulls. Remember everyone, we build cars for REAL WORLD conditions, not dyno queens with iced-down intake manifolds!
– You can download the manifold pressure and RPM datalogs logs from the Innovate LM1 and LMA-3 AuxBox by CLICKING HERE (RIGHT CLICK-> SAVE AS, then open with LogWorks program!)
– Please note that on the next two tests we will log a second wideband reading on the Innovate logger as well (we forgot to weld in two wideband bungs so we have one for dyno logging and one for our Innovate data logger), and are also trying to get the new Innovate OBD2 logger working on this car so we have data from the factory ECU! However there are multiple documented hardware and firmware issues with the Innovate OBD2 logger right now, so hopefully they will sort them out within the week!

Here are three dyno pulls in sequential turbo operation on three different boost levels, with the highest runs hitting 17psi and falling off to 16psi by redline. I didn’t mess much with boost controller on low boost to prevent the creep you can notice. I made a few pulls on the way to the dyno on high boost and adjusted the gain to get it fairly smooth, but obviously there is more room for improvement. I didn’t spend a ton of time on it since we just made a few baseline pulls and will be adjusting it later.
Sequential operation

Here is the air:fuel ratio and manifold pressure (noted as ‘fuel pressure’ but is actually manifold pressure) from the runs above. Also note that there is no smoothing, thus the lines being jumpy. On the Innovate datalogs and boost gauge, the boost was a smooth curve, so just brief disregard the boost spikes and valleys:
Sequential air fuel and boost

Here are the next three pulls which were made in parallel (AKA True Twin) mode:
true twin horsepower and torque

true twin air fuel and boost

_____________________________________________

SECOND ROUND OF TESTING:
- April 16, 2008
- Results are from a Dynojet 248C with SAE Correction (NOTE: MAP ECU tuning will be done on a Dyno Dynamics load bearing dyno, but we used the DynoJet inertial dyno for the horsepower readings because they are ‘glory’ dynos and read higher horsepower numbers that most people are used to…)
– Conditions via Weather.com were 1:45pm eastern time, 67 degrees F, sunny, 25% humidity, 30.29 in/hg and steady, 29 degree F dew point.
– 93 octane pump gas was used for these pulls
– The car was driven 45 minutes to the dyno, and the ONLY cool down time it had was while it was being strapped down to the dyno! We allowed 1-2 minutes cool down time (with the car still running) between pulls. Remember everyone, we build cars for REAL WORLD conditions, not dyno queens with iced-down intake manifolds!
– Since the first test we did, we have had TWO issues with our Innovate Motorsports logging system. First, the OT-1 OBD2 logger was bad out of the box, which is why we couldn’t get it to work! Also, the LMA-3 AuxBox just suddenly stopped working while I was setting it up to log the first dyno run. So, we are waiting on both the OT-1 and LMA-3 AuxBox to be repaired by Innovate Motorsports….ugghh bad timing to say the least.

Here are three dyno pulls in sequential turbo operation on three different boost levels, with the highest runs hitting 18psi and falling off to 17psi by redline. I didn’t mess much with boost controller on low boost to prevent the creep you can notice. It seems that the ‘low boost’ setting on the Profec may be messed up, as I can turn it up 3/4 of the way and it will only make 15psi of boost. However the high boost knob works, so I’ll just use it for now and get the Profec warranted by Greddy once the project is completed. This explains why the ‘low boost’ curves above don’t have more peak boost than with the controller off, however they do have the benefit slightly quicker boost response.

GT28R Sequential HP

Here is the air:fuel ratio and manifold pressure (noted as ‘fuel pressure’ but is actually manifold pressure) from the runs above. Also note that there is no smoothing, thus the lines being jumpy. On the Innovate datalogs and boost gauge, the boost was a smooth curve, so just brief disregard the boost spikes and valleys. 7psi at 2500rpm is great for turbos that have this much top end potential!

Also notice the ‘high boost’ run was shown on the boost gauge as hitting about 18.8psi and falling off to 18.3psi at redline, which is higher than the ‘high boost’ pull made on the original stock twin turbos. So, I turned the boost controller down a bit to the same boost level, and made one final pull (you will find this last pull’s dynograph as you read on…):

GT28R Sequential AFR

Here are the next three pulls which were made in parallel (AKA True Twin) mode:

GT28R True Twin HP

GT28R True Twin AFR

And, as promised, here is a final run I made at a lower ‘high boost’ setting. On the boost gauge it peaked around 17.9psi and fell off to 17.3psi at redline. So, this run was about 1psi higher than the ‘high boost’ run on the original stock twin turbos and made 29.8 rear wheel horsepower more. HOWEVER, a very interesting and promising note is that the air:fuel ratio (which is a direct correlation with ignition timing advance by the MAF signal and thus power production) on the GT28R turbos over 4000rpm is 10.0:1 to 10.5:1, whereas on the original stock twin turbos it was 10.5:1 to 11.3:1. If the air:fuel would have been the same for both the GT28R and stock turbos, the horsepower gains would have been a good bit more. Regarding lag, as you can see the GT28R turbos only have 100rpm more lag to hit 5psi, 250rpm more lag to hit 7psi, and 350rpm more lag to hit 16psi. The stock exhaust manifold is a major restriction on low boost over 6500rpm and on higher boost the stock manifold is very restrictive over 6000rpm, as I have seen on many cars including the Sound Performance budget single turbo kit that used the stock manifold with a 2-into-1 Y-pipe going to a single turbo….

SO, we have a lot of room to work with on the MAP ECU on our next round of testing, and it should yield great power gains by leaning the air:fuel (and thus advancing ignition timing advance) to very low 11’s at peak torque and trailing up to mid-11’s at higher RPM!

GT28R Sequential 17psi HP

GT28R Sequential 17psi AFR

_______________________________________________

THIRD ROUND OF TESTING:
- May 8, 2008
- Results are from a Mustang Dyno model 1750 with SAE Correction
– Conditions via Weather.com were 74 degrees F, rain showers, 56% humidity, 29.69 in/hg and steady, 57 degree F dew point.
– 93 octane pump gas was used for these pulls
– The car was driven 30 minutes to the dyno, and the ONLY cool down time it had was while it was being strapped down to the dyno! We allowed 1-2 minutes cool down time (with the car still running) between pulls. Remember everyone, we build cars for REAL WORLD conditions, not dyno queens with iced-down intake manifolds!
– During this dyno sesson compared to the last one, the only variable is that we installed and tuned the MAP ECU along with the HKS DLI ignition amplifier.
– We will update these charts ASAP with graphs that display an RPM range from 1800 RPM to 6700 RPM!

________________________________________________

FOURTH AND FINAL ROUND OF TESTING:
- May 16, 2008
- Results are from a Mustang Dyno model 1750 with SAE Correction
– Conditions via Weather.com were 68 degrees F, mostly cloudy, 65% humidity, 29.88 in/hg and steady, 55 degree F dew point.
– 116 octane leaded gasoline was used for these pulls
– The car was driven 30 minutes to the dyno, and the ONLY cool down time it had was while it was being strapped down to the dyno! We allowed 1-2 minutes cool down time (with the car still running) between pulls. Remember everyone, we build cars for REAL WORLD conditions, not dyno queens with iced-down intake manifolds!
– During this dyno sesson compared to the last one, the only variable is that 116 octane fuel was used and the boost was turned up.
– This dyno’s manifold pressure sensor read about .5-1psi LOWER than the MAP ECU’s logs. The LogWorks datalog below shows about .5-1psi HIGHER than the MAP ECU logs as I forgot to enter the current atmospheric pressure in it’s settings. The boost gauge on the car showed the same boost level on it’s peak hold as the MAP ECU logs.
– We will update these charts ASAP with graphs that display an RPM range from 1800 RPM to 6700 RPM!

Here is the 19psi (on MAP ECU log) pull, which yielded 480 rwhp and 473 rwtq:

Here is one of the 21.5psi (on MAP ECU log) pulls. The air:fuel at peak torque was a bit leaner than I wanted, even though there was a full 23 degrees of ignition timing advance which indicates no knock. Also, I could have leaned out the air:fuel at higher RPM, but again I tune for 100% reliability! I would estimate if the air:fuel curve was leaned out a bit more, the car probably would have made around 530-540 rwhp and 515-525 rwtq. But, the end result on this pull was 514 rwhp and 508 rwtq.  This first chart below shows the manifold pressure (PSI/boost), and the second one shows Air:fuel ratio.
Also, here are the LogWorks datalogs (RIGHT CLICK-> SAVE AS, then open with LogWorks program!):
CLICK HERE FOR DATA LOGS!



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