AFR discussions

I gave TVR Power a call and had a long chat with Jason about AFR who was very helpful.

He had discussed some of this with me when the run was done, but that was a long day and I must have missed some of it.

Summary seems to be:

  • It is running a bit lean, but not dangerously so
  • On a trackday in very hot weather with a low of WOT it may be more susceptible to problems
  • Normal and enthusiastic driving should be fine
  • A bit richer would give a little more power, but the injectors are running at their limits at WOT
  • There was no knocking on the dyno

Apparently the stock injectors from a 3.6 are fairly cheap disc type and over the years can lose some of their top-end flow. This may be quite common, but not many owners keep finding small things to fix like I do (brake bias, spring rates, AFR…).

As new it should have run at ~ 13.3 which is a favoured value, although they are fine a bit higher than that.

Solutions could be (from cheapest to most expensive)

  1. Remove injectors, clean and flow test. Then refit or use other 2nd hand injectors from stock if they flow better. This will not involve a remap and should only improve things from current.
  2. Fit cleaned / tested 2nd hand Red Rose injectors (£20 each, apparently good for 400 bhp rather than 340ish of stock). This would involve a remap, but might be a 1/2 day using an existing map as a base
  3. Fit the pintle type injectors as used in 4.3 / 4.5 builds (£114 each). Plenty of flow, full-map required.

We decided to try the first option when it is for a service in a couple of months time. Ready-made maps may not exist for a stock 3.6 with upgraded injectors as people seem to combine that with other engine work.

I am a bit less worried about it now, family life is conspiring against me doing a full trackday this year, but there might be a bit of driver training and some track test time for the brake bias changes and the new spring rates / geo that is being done at the moment.

Also had some comments from Neil Garner about this when asking about the suspension (dampers still with Gaz) who said that richer would give a bit more power but 14 / 14.1 isn’t too worrying.

Looking forward to getting the car back with some updated geo and springs, but we are currently using the garage for the dining room contents while some work is done, so it is a good time for the car to be on a Cotswolds holiday.

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