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.
Boost Onset
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.
Airflow
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.
Compressor Efficiency
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.
Pre-Turbine Backpressure
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.
Exhaust Gas Temperature
Temperature of the exhaust gasses before and after the turbine are about equal between these two turbochargers.
Power
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.
Conclusion
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.
TC Stg1
Functional Requirements Verification Matrix| 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 |
TC Stg1
Technical Requirements Verification Matrix| 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 |
TC Stg1
Supportability Requirements Verification Matrix| 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.
TC Stg1
Performance Specifications| 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.