Few months back I was at the dyno and came away very dissapointed with regards to the figures my FD put out on the dyno. With all the mods that I have in my sig it dynoed at 255hp (10psi) and 284hp(12psi) at the crank (not at the wheels). Intercooler was cold during there runs due to large vent in front of the car during the run. What I find most interesting is that how the power starts dropping before 6000RPM

Any comments?

 

Ahh... my sig

 

It is true that those figures seem low for your mods.... BUT how do numbers from a "dyno system maha lps 2000" compare to a Dynojet? How do you know this isn't a normal reading for an RX-7 with your mods on that brand of dyno?

The shape of the curve does drop off a bit early.... Are your plugs/wires good?

Do you have any quarter mile MPH (or KPH hehe) figures? I guess you probably don't do quarter miles... something like half a km?

Brian

 

no wideband??..

 

the maha dyno uses small roller pairs, resulting in high tire losses. the coast down test is used to figure fwhp, but it must be done twice to do correctly. even then, it only measures losses with no high hp transfer, so it will be low.

 

400km ~ 1/4 mi

those do seem low, you've got the mods to push more than 300rwhp on this side of the pond...

 

Well, we do have some official drag races every year and I will attend one soon - then I will know my 1/4mile time and mph (kmh). Btw. 1/4mile = 402m.

No wideband.

Besides this chart, I also got EGT readout regarding to RPM and HP curve.

Could it be that this particular system shows such low figures ?

Could it be that I had wheelspin on the rollers ? (I had no weight on the rear tires - e.g. noone sitting in the trunk)

Could it be I have bad plugs or wires ? Would that explain the power drop at high RPM ?

Or could the high RPM HP drop be due to the wheelspin on the rollers ?

So many questions...

 

One more thing - a friend of mine dynoed his tuned 300ZX which should be around 400hp with his mods. This dyno only showed him 320hp.

Are the torque figures correct ? Figure is in Nm though.
Is the highest torque achieved at "usual" RPM for an FD ? (352Nm ~ 260lbs/f of torque at 4800RPM on 12psi)

Any other observations ?

Thanks!

 

bump

 

Don't worry about it too much, I use the local MAHA one and it reads much lower than other setups. Like you I can't get close with my fly figures to what the US guys get at the wheels.

I'll be back at mine in 2 weeks and will try to remember to post up, but last time running a street port at 0.8 bar I made 282 fly, 214 at the wheels (on the road 0-100mph in 11.5 based on my datalogs, so the car was running fine).


One thing I will say is that stock cars make the manufacturers claimed fly figures on these rollers.

 

Yes, funny thing is that stock cars made pretty accurate numbers (well, mostly) - up to 160hp. My RX7 and that 300ZX were the only high hp cars there though.

Also, the dyno graph seems so normalized to me. For example - look at the transition point - usually there is 100hp difference on such modified cars, but here its only few hp.

 

Looks like a possible airflow (CFM) issue to me in addition to what others mentioned. Your torque is dropping off at lower rpms than it should be.

Could you post the EGT graph?

Are your double-throttle plates still in the intake manifold, btw?

 

Airflow issue ? What do you mean by that ?

I'm sure throttle plates are stock, as the car was completely stock when I got it.

I'll post my EGT graph later.

 

I've dug out my graph, and it is very similar. My power is still rising when yours is dropping off (to be expected given the porting I've got) but my torque curve matches yours near identically - while it does drop off at the same point (on mine) it levels out again for a bit before dropping off completely.

I haven't seen a stock FD running on these rollers, but will do in a couple of weeks as we've got 7 FDs (in various states of tune) booked on for the same day. If I don't post up drop me an e-mail and I'll let you know how things went.

As a side note my air temps went through the roof last time (bonnet open with fans blowing in the front) which I only knew about after looking at the logs from the PFC. Next time we are going to do the run with the bonnet down and see if it improves air flow. Also running on a different set of rollers in 2 days time, so I'll be able to say how they relate to one another.

Stock cars all seem to be close on fly figures (examples I remember) - 218bhp scooby got 218.5bhp, 276 scoob got 269, 276 Evo got 290, 326 Supra got 323, 172 Clio got 180. I have also seen modded cars get figures such as a 526bhp Skyline.

 

Roberto, thanks ! I will PM you in end of february or so.
Robertio, do you also do PFC tuning on that dyno ?

Any other thoughts ?

 

All my mapping has been done on the road, I did consider doing mapping on the dyno but it is too expensive (IMHO), and needs to be modified when on the road anyway, so just use the road in the first place.

Ideally I'd go for limit free German autobahn as watching out for police cars tends to make the mapping process a little more stressful than it needs to be

 

Lol!

Where did you get the knowledge how to set the injector duty cycles and ignition timing ? I hope not trial & error

 

I try not to get knowledge, it just leads to people asking questions I went for the approach of leaving a mate to do the trial and error method up until his engine went pop, then getting a safe (read not the one that killed his engine) map from him (thanks Max ). Then using a wideband - added and removed fuel to get a recognised safe AFR setup across the rev range. It may not create the maximum possible bhp figure, but (up until now) it has worked fine, everyone seems to have slightly different opinions on the best way of mapping rotaries anyway.

 

Ok, AFRs I understand, but how in hell did you know how to set timing ?

 

Ok, this got a little off-topic

Any other opinions on the graph ? I will change my plug wires. Any other reason, the power would start falling that early ?

My boost is fine up to redline.

Oh... this is a BUMP

 

Right, but you know you it's much easier to put 10 psi through a straw then it is to put 10 psi through a 3" pipe. That's why I mentioned a possibly airflow issue.

EGT graph would be good though.

 

Yes, they are still in the intake manifold. Can one remove them ? Any side ill effects ? What purpose do they serve ?

I will be installing full 3" exhaust soon as I have a stock sized MP and some shitty catback with crush-bent piping on the car atm. Funny thing is that just before muffler there is a horrible crush bending, its only maybe 2" in diameter. I think this is a big bottleneck. I also had 2"1/5 diameter restrictor plate in the car at that moment.

In the meantime I also installed new plug wires, new plugs along with some new grounds and PFS IC.

After I'm done with exhaust I will go to the dyno again and hopefully "gain" few ponies

Thanks!

 

What was your A/F ratios, could you have been running to rich...

 

We didnt measure AFRs. I dont have 2nd bung in the DP.