Why new injectors?

As I understand it, the standard injectors are capable of flowing enough fuel for standard or mildly tuned engines (say up to 30-40 bhp over standard). To go beyond this you need to raise the fuel pressure or fit bigger injectors, and the standard injectors don't respond well to raised fuel pressure. Mark Adams, who does the vast majority of RV8 tuning for TVRs, recommends some Bosch injectors which provide extra flow and also better fuel atomisation. The improved atomisation alone seems to be worth 5-10 lb-ft from what I've seen.

Hi,
I will test mine once I get the engine out of the TVR for flow rates, it will be interesting to see what the Duty Cycle is like at max rpm and 12.5 afr,
Phil

the reason I was confused was that I have flow tested an awful lot of rover injectors, and after 100,000 miles I have found that they are getting near the end of their life, that means they are giving 95% of their original flow rates. The latest Bosch injectors have mulitple holes for better attomization, where as early ones dont, but that changed in the early 90's so I would think vertually all 5.0 TVR engines would have the later types and the injectors would be good for 100K, unless they are not capable of the 320BHP that TVR reckon the engines develope. But I would guess they must be, without flow testing a set I couldnt tell you. So untill you get to 320 BHP then why replace them, thats what struck me as odd. Im just trying to figure out what will need to be replaced in order to tune the 5.0 engine Im getting for the cobra. Hopefully within the next week I should have it home and start having some answers for my questions,
Phil

Yep there are ome cheaper ones about, Paul at Austec was telling me about them on Saturday

The fashion for Injector replacement puzzles me a bit. Took my 98 Griff to a one of Mark Adam’s haunts for a go on the rolling road, I was interested to get a reference point before considering upgrade options. They declined to do a “ Power Run” because the engine was pinking, I couldn’t hear it but apparently they could. Without any investigation other than timing the recommended cure was Bosh injectors, Bosh AFM and re-map by MA. On returning home I whipped out the plugs and if anything the engine it running rich on all cylinders not lean.

Where I can believe that substantial induction and cam changes may require a higher flow rate to properly fuel the engine I find it difficult to believe that all the 5l engines were shipped with the injectors at their limit, which is the argument made by some. Several articles I have read indicate that flow rates should be chosen so as to allow them to be fully open, if the flow rate is too high they have to be opened and closed so quickly they never really achieve fully open. Landy specialists report very little issues with the Lucas part even on high mileage engines.

A cynic may wonder if the bigger injectors are frequently recommended to some degree by the need to have a re-map on a rolling road, oh and while you are at it perhaps some induction mods would be good, that’ll be £2500 thanks.

It would be very helpful if some of the apparently many 5l owners who have the bigger injectors would report the result on here. If the results are worthwhile I am happy to spend the money but don’t want to be a fashion victim. I have asked the question on here before and mostly got "not really worth the money" reports directly by email.

steve-v8s said:

A cynic may wonder if the bigger injectors are frequently recommended to some degree by the need to have a re-map on a rolling road, oh and while you are at it perhaps some induction mods would be good, that’ll be £2500 thanks.

nooo, no one would ever do that surely !

Anyhow, if we knew the flow rates then its very easy to work out what power they will be able to fuel. Most injectors opeing times are around 1mS or less, depending if they are high impedance or low. So at 6000 rpm you have 10mS to add the correct fuel, so at 85% Duty Cycle thats 8.5mS remove the opeing time, 7.5mS of fuel, your right about running higher duty cycles, I have run at 95% on the 3.5rover items without trouble and I know of several people who run at 100%. Will be interesting to see what flow they give,
Phil

From my understanding its not the flow rate thats better on the bosch injectors from the standard lucas ones, its the spray paettern/mist that is delivered much better.
After seeing both perform next to each other in an injector cleaner, the bosch ones produced a nice mist and the tubes filled up without seeing a jet of water going into the tube as filling up. The lucas ones produce more of a jet and less misting(new ones en all).
I am also led to understand the way the petrol is pushed through the injector on the Lucas ones over time can wear over time making a even worst jet. cleaning can help but not always. Where as teh Bosch ones dont wear in the same way I am led to believe.
I think the ones MA was hoping to get where a batch from a certain car(leave to him to say) that he found in the USA.

BB

As a company who doesn't supply injectors or financially benefit from the sale of, I feel that i can offer an unbiased view point.

I have seen very good results from the fitment of Bosch injectors in many applications, Austec and Mark Adams sell them when appropriate, by this i mean when a significant gain would be achieved, i have seen many cars where the standard injectors were "maxxed out" and potential power just couldn't be achieved,

I know that some well respected engine specialist don't "go along" with the upgrade injector route, but all i can say is that i've seen good results on many occasions.

I think in a past thread Mark did reveal a part number but to be honest it's no use to the masses as there are no cheaper outlets for these injectors, the trade mark ups are believe it or not quite small, i agree that they have been too expensive and fortunately Mark & Austec have worked hard to get a better deal with a new injector.

The best thing is to discuss any fears or concerns with Mark or Austec i'm sure you will get a satisfactory answer /service.

2 sheds said:

As a company who doesn't supply injectors or financially benefit from the sale of, I feel that i can offer an unbiased view point. The best thing is to discuss any fears or concerns with Mark or Austec i'm sure you will get a satisfactory answer /service.

......fabulous answer Tim! I remember the 'emerald ecu' thread you joined in on a little while ago,when you appeared to get a little upset about my highlighting the very low business ethics that 'some' companies have.Whenever i used to call you,the only other persons or companies you would mention,were Mark Adms,or austec.If you speak to MA or Austec,guess what,oh yes,its that cosy little circle again isnt it?Its such a shame that so many dont realise just whats going on isnt it?ps.have you seen the joospeed website lately?hmmmmm,now theres a good example of business ethics yet again THE BEST THING ANYONE CAN DO IS GET AN UNBIASED POINT OF VIEW!!!

My racer was recently on the rolling road and ran out of fuelling even with higher fuel pressure available. It's a 2.9 24V Cosworth twin turbo. Standard injectors ran out at about 260bhp. I had a set of 'barely used' Bosch injectors fitted (£30 each) as used in the noble cars and an uprated Bosch fuel pump (£160) which are good enough for 450-500bhp. The injectors were great value for money and even new would only sell for about £60 each. Very tempted to try these on the Cerb, if 6 are good for 450ish bhp then 8 may suit the AJP8 very well. I'm very interested to know whether this injector stuff actually adds any bhp or whether it's just a very clever marketing ploy to extract more money from TVR owners. My money is on the latter cos I've seen loads of hyped up figures for most TVR upgrades, most recently Cerbera induction with absolutely absurd gains quoted (from experience approx 4 x what you'd see in reality)

Numers eh! You just gotta love em!!!!!!!

Ceejay