|
|
-
How much motor is too much motor?
The basics: 2015 GRT running USMTS/USRA rules @ Devils Bowl in TX. This car is new and just assemble over the winter, it now has a total of 4 race nights on it. The setup is GRT by the book with exception of RR spring is 220# instead of 175#, RR upper bar is up one hole. These two differences are based on 20+ years of setting up cars @ the Bowl and being a very consistent top 5 - usually top 2 car. In modifieds and late models ( LMclass dropped in 2014 and sold out LM cars and all related items). The % numbers are 56.4% rear and 54% LS.
So here seems to be the issue, our motor is an "Open" motor, 3.875x4.155, roller cam, 14 degree Pro-Action aluminum heads. On a conservative dyno is was 752hp, I do not have the spec sheet with me and will post it later tomorrow when I am at the shop for more complete numbers. Prior to this season in our "older cars" which consistened of a2001 Smileys, 2005 Dirtworks (2 time champion car) a 2009 Shaw and recently a 2012 Skyrocket. Motorwise always had either basic 3.75 stroke x 4.04 383 w/ Motown heads, a couple of different 3.75x4.125 w/ similar heads and last seasn a USRA spec head 3.875x4.125. I could look up the dyno sheets but as I recall about 600 was the best of any of them.
So the problem we are having with these motor is it is a tire spinner, just no take off on starts or re-starts. Last night started 2nd row inside heat and car went nowhere, by the time it was too late the best was a 5th place finish. Started 5th row feature, went back to 9th then he got the momentum going and got to 4th and was closing on 3rd. A caution and re-start with 3 to go ruined that - went backwards and finshed 9th.
I will answer any more details or info I can, but like my title askes, is this maybe just too much motor for this class of car. We went to it because last season the Spec motor lacked a little on a typical Devils Bowl heavy track. Would lead heat races but at the end have one the open motor cars have just that little bit more.
Any thoughts, ideas or suggestions?
-
Where did it peak and how many rpms are you turning it? That's a lot of motor for a 8in tire. It might take a couple dyno trips to get it smooth enough to drive.
-
-
Willy's carb shop makes a adjustable restrictor plate.
I would suggest it. get it set where it is drivable.
on a side note that kind of motor is common here in UMP country. most have no problems hooking them up. but we have a better tire for it, but we do not get any longevity out of them.
I think there should be lifeguards in the genepool.
-
That is the reason that the 604 crates are winning so many IMCA races. I would say you are way over powered. I would say your car would be better with those old motors you had.
-
WAY too much power for that tire. period
-
Birdcage index is: 0.5* up in front on RR -- 0.5* down in front on LR.
-
Here are the dyno numbers by the hundred starting at 4500rpm, first is Trq and next is HP:
4500= 634.6 557.7
5000= 665.8 646.5
5500= 663.1 705.8
6000= 644.9 751.3
6500= 604.2 756.4
7000= 558.7 750.7
7500= 513.9 732.7
-
-
Already taken gear out, was 5.28 with spec head and down to a 5.11 now. Going to index the LR into the spring more. I will check into the plates.
-
-
Like when you do a comparative, Puts it in perspective. JMO
-
Unless he is a cushion banger like a davenport style i think you are going to really struggle. Might be better off to put the spec in for a couple weeks and see if it helps.
-
Are you running a pull bar or lift arm? May need to adjust for a stronger motor. As well as do some shock tuning
Bill W. and Dr. Bob......who could have known.
-
It is a pull bar. Long Quik Car with all red bushings - NEW.
-
Try going with a softer bushing. That would allow it to absorb some of the torque rather than transferring it to the tires. Or you could lower the entire pull bar a little bit
Last edited by Confused?; 05-10-2016 at 06:10 PM.
Bill W. and Dr. Bob......who could have known.
-
Just throwing this out there, but this sounds like this could be a driver issue with this bigger motor. In your post you say starts and restarts he struggles, but in the feature he was closing in on third. That makes me think he's too hard on the throttle on starts and restarts, but settles down on longer runs. Maybe just needs more laps to get used to this motor. JMO
-
-
This motor came about because of too many second places last season (it was a short season for us). We decided over the winter that we would go back with something that would give more on that big track than our spec head motor was doing. Maybe we over did it a little. But for those that have never been to the Bowl it takes some HP to be a top car there.
-
never saw a car with too much motor, but I have seen plenty with the throttle too far open!!!!!
Posting Permissions
- You may not post new threads
- You may not post replies
- You may not post attachments
- You may not edit your posts
-
Forum Rules
All times are GMT -5. The time now is 08:31 AM.
|
|
Bookmarks