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Frequently Asked Questions - Vauxhall Corsa
 
Performance gains from new cams
Group A Rally car intake restrictions
 
Performance gains from new cams

Question: I currently own a C20XE Corsa b with an early 1990 engine. I have a manifold back system on the car at the minute and I'm looking into a new exhaust manifold (needs a hole for the lambda) and maybe cams. Please can you give me some advice.
Also I have a X14XE engine that i plan to put into my other Corsa b. The head has been skimmed, so could I fit new cams? I've heard you can get big gains from a new inlet manifold?

Answer: Because our range of products is so large, it's impossible to provide a quotation based on the information you have given. What I will do is to give you some information on what I advise the direction you should go in.

We do not produce camshafts that are direct replacements on the GM range of engines. There are many reasons for this, the main ones are that there is insufficient room to get a big enough profile into the engine without modifications that can produce any worthwhile performance gains & secondly any cam profiles that are big enough to produce a gain completely upset the standard air flow meter systems & management systems.

My suggestion would always be to replace the standard management system with an MBE system, this will allow you to tune the engine without the restrictions imposed by the standard system & I would normally suggest the fitting of throttle bodies provided your installation will allow it. This will give a huge improvement in performance & in most installations a nice engine to drive. This allows the engine to breathe properly, then camshafts & modifications to accept them can be added later, whereas adding the camshafts first would be limited by the intake & the exhaust system.

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Group A Rally car intake restrictions

Question: We have built a Vauxhall Corsa B 1.6 16V C16XE grA rally car a year ago. On this engine we now use a cams set with Inlet 12.00mm lift, 288deg, 3.7mm lift @TDC, Exhaust 10.5mm lift, 284 deg, 3.2mm lift @TDC. As the car is grA we need to keep the OEM inlet manifold and throttle body and the OEM exhaust manifold. The torque of the engine is 16.7Kg m @ 5200 rpm and the power 161bhp @7400 (rolling road test). Since the cams are relatively big but the peak torque rpm point is low we wonder if there is potential to this engine to move the peak torque point 1000rpm higher (as is the case with the Peugeot 1.6 16V engines) and peak power at 7800-8000 rpm so as to improve high rpm range performance, or there is something (for example the inlet manifold) that will not allow this.

Answer: We have not worked on Group A Corsa engines for more than 10 years, the intake system is the biggest restriction & is one of the worst we have seen. This is the part that holds the power back in comparison with better intakes, such as the Peugeot. We did use much bigger cams than you are using & although the engine produced slightly more peak bhp, in our opinion the engine generally got worse meaning less driveable. Unless you can replace the intake system, your options are limited.

Our customer replied: 'Thank you for your e-mail. The customer had said that he would use this engine for one year just to get familiar with the car and develop the chassis and then he would go for a kit car spec engine with throttle bodies etc. so we did not spend time flow testing the head, intake etc. But the data I had during mapping and then on the dyno showed that something does not allow the torque to go at high revs and cam timing changes affected low but not high rpm performance. We tried a bigger exhaust but things were the same if not worse. So the only thing that was left to blame (we had a bad feeling for the intake from the beginning) was the intake which is very long with small chamber volume and many curves. Your e-mail confirms this impression. Thank you for your feedback.'

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