After market spark plugs dyno test.

[Russ M]

Guys as promised we just finished dynoing my viper with some after market plugs to see if there was any truth to the rumor that stock plugs are best. Well let me be the first to tell you that it is completely false.

The plug we tested was 1 step colder than stock, which is good considering that the factory plugs are a bit too hot. It may be that a hot plug like the factory in an Iridium would make considerable power gains, but they are not made. Hence we will have to live with this colder plug. And the power output was smother and better in the upper rpms.

Now don't run out expecting to gain lots of hp with different plugs, that won happen unless your Viper is so modified that a better spark is needed. But you can expect to have a plug that will last much longer than the factory junk, and one that will give you 2-3 hp gains in rpms above 5200.

All the testing was done with letting the car come to the same temperature range and pull was made. 3 pulls were made with each plug and all 3 in both tests were virtually identical.

The guys at Denso were just as curious as we were on what the results would be, and they are very happy with the results as I am. These were the full Iridium tip plugs and are definitely not a cheap alternative. But for many of you that have considerable mods done to your car may benefit more than you think by running these plugs.

My Viper only has exhaust/no cats/k&n's, smooth tubes/25% under drive pulley. So a viper with headers/headwork/Nitrous/etc.. could gain considerable power.

Please no flames, this is just a test I wanted to do my self. I have nothing to gain except a better running Viper.

 

[utahviper]

What were the plugs that gave you the best result? Brand and part number would be very helpful. Do have any dyno graphs you can show us to compare?
Thanks Todd

 

[Russ M]

Todd,

The only plugs tested were stock and Denso Iridiums(IQ20). By your signature I am guessing that your car would be a very good car to try these on due to the power out put. Please let us know if you do install them how the car feels, and also dyno numbers if you dyno it.

I did not get a print out of just the spark plug results, only plugs and underdrive pulley together. And I have that if you like comparing it to prior pulls.

 

[Joel]

I'm particularly interested in this since I sell Denso plugs through my shop and have done so for about 12 years. I believe the correct number in Iridium for a standard viper is IK16, which I would like to try in my GTS, but given the price even at wholesale level, I want to be sure they'll be better than standard. Also Nadine and I will be fitting her supercharger later this summer and we anticipate that a change of plugs and possibly heat range may be beneficial given the higher cylinder pressures and changed temps and mixture conditions. Why did you use the IQ20 instead of the IQ16, IK16 or IK20 and did you notice any difference to the running such as smoother idle etc. Also do you think that the cooler running 20 heatrange will be more prone to fouling in slow running conditions ? My feeling is that the IK16 is best on the standard or lightly modded engine with IK20 being better on the heavily modded or supercharged motor.

 

[Russ M]

Joel,

I know the guys over at Denso fairly well, they have been working with me on plugs for years on my race cars. The IQ20 was used because that is what the book calls for, and there is no IQ16. The car runs about the same at idle, and feels smoother while reving. However this could be false information since the comparison was not made to new champions.

 

[99 R/T 10]

What was your final numbers? HP&TQ?

 

[Henry Cone]

Russ, do I understand your post correctly - that you compared new Densos against used Champions?? That is what it seems based upon your last post. If so the test does not seem to be one that allows a conclusion that Densos are better than Champions to be made....

 

[Russ M]

Henry,

After I posted that I knew that someone would think that. That is not the case, the power figures used for comparison were made before with new champions. Just that when I changed them out they were old and could affect the car idle/ride.

Wilddude,

439.6 hp and 474TQ

 

[Joel]

Russ

In my European Iridium catalogue (the latest), IK16 is listed for the viper and I'm almost certain that IQ16 is available, I'll check later when I get to the shop and come back with info. I would worry that although the colder running 20's would give a good performance on first installation, slow running in a road car may cause them to foul up and a deterioration in performance. Probably better for hard track use though.

 

[Russ M]

Joel,

I talked to Aaron at denso the other day about them listing 2 different plugs for Vipers, and we came to the conclusion that it must be a mistake.

This is because according to the book it saying that Vipers used 2 different types of plugs over the years, and that is not the case.

Please let me know if you come up with something different.

 

[Joel]

Hi Russ
I'm back after my day at the shop and here is the information that may be useful to your Denso tech
IK16 is the plug listed for the viper, Denso stock no 5303#4 and bar code no 042511053038.
IQ16 is stock no 5301#4 and bar code no 042511053014.
This info is lifted straight from the latest iridium plug catalogue, IK16 I already have in my shop, IQ16 I will know about tomorrow from Denso Europe in Holland. The IQ plugs conform to JIS standard and the IK plugs to ISO standard. The difference is in the length of the ceramic body where the plug cap fits on, IK plugs having a slighter shorter length, by a couple of mm, the purpose of this being to fit different types of plug cap seal and of course body length is important where an ignition pack is fitted dirrectly onto the plugs as in many 4 cyl 16v recent motors.
Anyway hope thats useful and I feel sufficiently fired up to try a set of IK16's in my Viper, I will post on my SOTP impression.
Let me know how you get on with your trials

Joel

 

[Joel]

IQ16 available and on the way from Holland. If you need any email me
Joel