| In any discussion about turbocharging, the issue of | | | | increased the possibility of reversion. In essence, it |
| turbo lag is sure to rear its ugly head. For many, | | | | reduced the engine's volumetric efficiency, further |
| turbo lag is a major issue but the issue of turbo | | | | robbing the engine of power and performance. |
| lag is greatly misunderstood. No, turbo lag is not a | | | | Again, these deficiencies in performance were |
| myth, and yes, it does exist - in technical terms, | | | | only overcome when the turbo started producing |
| turbo lag can be defined as the time it takes the | | | | post pressure. |
| turbo to spin fast enough to produce boost | | | | With a much lower compression ratio, increased |
| pressure. However, it is not as bad as most | | | | back pressure and reduced volumetric efficiency, |
| people believe. | | | | an OEM turbocharged vehicle was often out |
| The problem originates in the 1980s when turbos | | | | performed by its naturally aspirated brethren in |
| and superchargers became so popular that | | | | those precious few seconds while the turbo |
| several marques started producing OEM turbo | | | | spooled up to spin fast enough to produce boost |
| vehicles like the 1983 Nissan EXA Turbo and the | | | | pressure. Once the turbo spooled up and started |
| Mitsubishi Colt 1600 Turbo. With these vehicles, | | | | creating boost pressure, it more than |
| the issue of cost and reliability was more | | | | compensated for the deficiencies caused by the |
| important than performance. In a sense the turbo | | | | lowered compression ratio and lowered volumetric |
| was more of a marketing gimmick as a 78 kW | | | | efficiency. |
| turbocharged 1500cc motor cannot be described | | | | But today, with the advances in turbo technology |
| as a performance vehicle. | | | | and the use of an intercooler to remove some of |
| There are two things these manufacturers did to | | | | the heat that is a natural side effect of |
| give turbo lag a bad name: to minimize costs they | | | | compressing air, it is not necessary to lower the |
| produced turbocharged vehicles without | | | | compression ratio. Indeed, with the proper use of |
| intercoolers and then, to deal with the increased | | | | an intercooler turbocharging has become a bolt-on |
| temperatures of the compressed air that was | | | | accessory with no need to open the engine. Also, |
| pumped into the combustion chamber, and to | | | | because you don't need to get boost pressure so |
| minimize detonation, they lowered the engine's | | | | quickly, you can run a slightly larger turbo that is |
| compression ratio. The Nissan EXA Turbo, for | | | | better suited to the exhaust system and |
| example has a compression ratio of 7.4:1 | | | | produces far less back pressure. This effectively |
| compare to the normally aspirated engine's | | | | takes turbo lag out of the equation. Even though |
| compression ratio of 9.0:1! This robbed the engine | | | | the turbo will still have turbo lag, the engine's |
| of power and performance that was not | | | | power and performance is not compromised by |
| compensated for by the turbo until the turbo | | | | lowered compression ratios and increased |
| spooled up and started producing boost pressure! | | | | backpressure. |
| Fortunately, these vehicles were also fitted with | | | | So the use of a properly sized and efficient |
| small turbos so they spooled up quickly enough, | | | | intercooler should be a compulsory part of any |
| but the small turbo also contributed to | | | | turbocharger system if you do not want to |
| backpressure in the exhaust system. This | | | | suffer the consequences of turbo lag. |
| affected the exhaust's scavenging ability and | | | | |