The turbochargers that I intend to try out with the Mamba wastegate actuators are the Frankenturbo F21 retrofits. This evening I installed the Mamba wastegates to see how well they would fit on the turbochargers.
The new wastegate actuators fit onto the turbochargers without any problems.
So far I am impressed with the Mamba product, it looks well constructed and the initial fitting went well.
Next up I am going to play around with the preload spring options.
Since I last gave a look at the FrankenTurbo F21 there has been an update made that legacy F21’s can take advantage of. As FT has developed a turbo for the BMW N54 engine the legacy F21 turbo’s can be retrofit with a similar product that leverages the work being done for the BMW engine.
I came across an old pair of F4H turbo’s that were ready to be rebuilt and I contacted FT to see what could be done with them.
The turbine housings were appropriate to reuse with the latest turbine wheel so I shipped those off to Swaintech to have their White Lightning ceramic coating applied.
After the coating was applied they were forwarded to FrankenTurbo for the update.
Now that the turbochargers are back with me they’ll be on the shelf while I make my way through a number of projects.
The changes that this version of the F21 has are:
The change to using this design with legacy (original F21 compressor wheel) rebuilds started around summer of 2017.
The Turbo Concepts Stage 1 turbocharger was a late entry in my effort to find what I thought would be the best stock motor turbocharger. When I ordered the stage 1 turbochargers it was with some expectation that the vendor’s claims for the product would be met, or at least would be close to being met. Those claims were to be capable of out-flowing an RS4 K04 by 20%, have a strong low-end response, and reach up to 450 wheel horsepower on pump gas.
After purchasing the turbochargers and while I was in process of installing them on my S4 the vendor revised the target horsepower downward substantially, to a new expected value of 380 whp. When I inquired about the boost level to run the turbochargers at the recommendation was a boost level similar to that of a conservative K04 tune. Based upon the vendor’s statements about the product the Turbo Concepts Stage 1 turbocharger is not going to be competitive in my search for the best stock motor turbocharger. It is more likely that the Turbo Concepts Stage 2 or 3 turbo would be a contender for the best stock motor title.
The TC Stage 1 turbocharger does present a good alternative to the BorgWarner K04, and that is what I am going to show some comparison data with.
The TC Stg1 turbo’s response is close to the BorgWarner K04’s. It needs to be noted that I have not had the opportunity to log the TC turbo’s under warm weather conditions. Based on the slower response that comes with warmer weather I would expect the Turbo Concepts results to expand upward slightly if data were recorded during summer conditions.
Not withstanding the partial data shown above, the TC turbo’s are performing well. The difference in responsiveness between the TC’s and K04’s is quite small.
I have not logged any meaningful increase in airflow from the Turbo Concept’s turbos as compared to K04’s operating under similar conditions. This is not surprising, the TC compressor wheel is only slightly larger than a K04 compressor.
The efficiency of the compressor wheel, estimated from the rise in the charge air temperature passing through the compressor housing, is better with the Turbo Concepts turbo. The charge air temperature exiting the compressor ends 60-70 degF cooler with the Turbo Concepts Stage 1 turbo’s.
For an equal intake manifold pressure (boost pressure) the Turbo Concepts turbos have a higher pre-turbine pressure in the exhaust manifold. Higher exhaust back-pressure in this situation is not desirable.
Temperature of the exhaust gasses before and after the turbine are about equal between these two turbochargers.
Lately I’ve skipped taking the S4 to the dyno to record data for turbocharger comparison purposes. With the variation that arises from shop temperatures and tuning the outcome is potentially less clear than measuring more ‘raw’ data.
On the street I am recording similar FATS times with the TC Stg1 turbo’s as I did with K04’s. Again though, environmental conditions and the tune come into play, but with quite a few pulls on each setup having been conducted I feel these two turbochargers produce similar FATS times.
Long term reliability will remain a question for some time, and determining a preferred boost profile is something that the vendor will want to give some attention to. Overall the Turbo Concepts Stage 1 turbocharger performs very well when compared with the BorgWarner K04 and is a cost-effective alternative that has delivered K04-like performance on my S4.
| Number | Functional Requirement Description | Verification Method | Pass / Fail |
|---|---|---|---|
| 1 | Rapid acceleration at 2000-3000 rpm. | Demonstration | Pass |
| 2 | Maintain strong acceleration from 5500-6500 rpm. | Demonstration | Pass |
| 3 | Biturbo configuration. | Inspection | Pass |
| 4 | Does not require unique parts. | Inspection | Pass |
| 5 | Equal or exceed RS4 K04 performance. | Test | Fail |
| 6 | N75 DC <80% at 6800 rpm | Test | Pass |
| 7 | Wastegate modulation of boost at part throttle. | Test | Pass |
| Number | Technical Requirement | Verification Method | Pass / Fail |
|---|---|---|---|
| 8 | Charge air temperature < 300 degF | Test | Pass |
| 9 | Exhaust back pressure:Manifold pressure ratio <= 1.5 | Test | Fail |
| Number | Supportability Requirement | Verification Method | Pass / Fail |
|---|---|---|---|
| 10 | Reputable vendor with good product support | Demonstration | Fail |
| 11 | 12 month warranty | Inspection | Pass |
| 12 | Cost competitive with alternatives | Inspection | Pass |
| 13 | Price not greater than 20% over RS4 K04 | Inspection | Pass |
The TC Stg1 product Fails the reputable vendor requirement due to the short period of time that Turbo Concepts has been providing products for the B5 S4 platform, there is insufficient information available at this time to award a Pass.
| Number | Specification Description | Verification Method | Pass / Fail |
|---|---|---|---|
| 14 | Develop 20 psi of manifold pressure by 3100 rpm | Test | Pass |
| 15 | 2-11 psi time should be <= K04 time at all rpm | Test | Fail |
| 16 | Maintain >= 25 psi to 7000 rpm | Analysis | Pass |
| 17 | <= 45 psi of exhaust back pressure at 6500 rpm and 25+ psi of manifold pressure. | Analysis | Fail |
| 18 | Mass Airflow Rates >= 375 g/s at 6000 rpm | Test | Pass |
| 19 | FATS time <= 3.5 sec (Sea level, 60 degF) | Test | Pass |
| 20 | Torque >= 400 ft-lbs | Test | Pass |
| 21 | Wheel power >= 400 whp | Analysis | Pass |
| 22 | MTBF >= 48 mo. or 50,000 miles | Analysis | Fail |
The TC Stg1 turbo Fails the MTBF requirement due to the short period of time that the product has been available. There is insufficient user information available upon which to base awarding a Passing score.